GB2215771A - Magnetic latch device - Google Patents

Abstract

A latch device includes a magnetic substance (3) secured to a door (1), magnet means (7) received in a casing (4) secured to a body (2) so that it can project from and retract towards the casing, be spring-biased in the projecting direction and be magnetically coupled to the magnetic substance, a slider (8) received in a juxtaposed relation to the magnet means in the casing so that it can project from and retract towards the casing and be spring-biased with a projecting force greater than the magnetic coupling force between the magnetic substance and the magnet means, movable engagement means (26) spring-biased to hold (at 27) the magnet means in a retracted position when the door is pushed towards the body (fig 3c), and releasing means (28) coupled via a shaft (23) to the engagement means (26) and engaged by means (29) on the slider when the slider has been projected by more than a predetermined extent. <IMAGE>

Description

LATCH DEVICE This invention relates to a latch device for holding a door such that an opening in a body is closed thereby.

There are various types of latch devices for holding a door hinged to a body by a hinge in a closed state.

For instance, there is a so-called floating latch, in which a cylindrical body is provided in a latch casing secured to a main body so that it can project toward and retract away from a door and is spring-biased in the projecting direction, a pair of engaging pieces which can be disengaged when the cylindrical body is projected and which can be engaged when the cylindrical body is retracted are pivotally provided in the cylindrical body, and a striker consisting of an engagement projection capable of engagement with these engaging pieces is provided on the door. In this floating latch, when the door is closed, the cylindrical body is pushed by the engagement projection to cause engagement of the engaging pieces with the engagement projection in a sandwiching fashion. The cylindrical body is provided with locking means of a so-called heart cam type and can be held in a retracted state.Thus, every time the door is pushed, the state of engagement or disengagement is held. Thus, it is possible to effect opening and closing of the door.

However, in such case, with aldoor that is opened and closed frequently, play will develop in the door hinge(s) over long-time use. In such case, when the door is closed, the engagement projection and engaging pieces will be offset from each other, so that it is no longer possible to obtain a satisfactory state of engagement between the two. The engagement projection is liable to be broken when the door is closed.

To cope with these problems, there can be used a magnet type latch having a magnet secured to the main body and a plate-like magnetic substance fixed to the door. This arrangement increases the magnetic engagement surface of the magnetic substance so that the positional deviation between the magnet and magnetic material can be tolerated. However, since the magnet is fixed in place, the door must be opened by pulling it. This means that it is necessary to provide a grip or the like on the outer periphery or front of the door, thus increasing the cost of manufacture of the door. Further, when opening the door, it is necessary to pull the door with a force sufficient to overcome the magnetic force of the magnet.

Further, there is another latch device having the aforementioned heart cam structure, in which a magnet is secured to a projecting end surface of a cylindrical body which can be projected and retracted, and a platelike magnetic substance is fixed to the door. With this structure, the door can be opened and closed by merely pushing the door. Thus the operability is improved.

However, it is necessary to provide a comparatively long stroke of the cylindrical body because the door has to be opened by pushing the door with the projecting end surface of the cylindrical body to separate the magnetic substance from the attraction surface of the magnet and cut the magnetic flux between the two. Thus, it is necessary to increase the size of the heart cam structure cn the flagnet side. Further, when closir.c the door, it is necessary to push the door.

The present invention has been accoirplished in the light of the above, and the primary object of the invention is to provide a latch device which can readily hold a door in a closed state even if positional deviation is produced when the door is closed and which improves the cperability in opening and closing the door.

According to the present invention, a latch device for use with a door movable relatively to a body comprises a magnetic substance secured to one of said door and said body, magnet means received by a casing secured to the other one of said door and said body so that it can project from and retract towards said casing, be spring-biased in the projecting direction and be magnetically coupled te said magnetic substance, a slider received in a juxtaposed relation to said magnet means by said casing se that it can Fvrc,ect fror and retract towards said casing and be spring-bIased with a projecting force greater than the magnetic coupling force between said magnetic substance and said magnet means, movable engagement nears spring-biased te hold said magnet means in a retracted position, and releasing means for releasing the state in which said magnet means is held by said movable engagement means when said slider projects more than a predetermined extent.

With the latch device according to the inventIon the door can be held in a closed state by merely causing engagement of the magnetic substance and magnetic means with each other. Thus, ever, if a deviation is produced between the relative engagement positions of the magnetic substance and magnet means, the two can still be engaged with ease. The door is opened by pushing it in the closing direction This causes the magnetic substance and magnet means to retract temporarily, but the magnet means is held in a retracted state until the projection of the slider is completed.

Thus, the door can be opened smoothly.

The other objects and characteristics of the present invention will become more apparent to those skilled in the art as the further disclosure of an exemplary embodiment of the invention is made in the following detailed description with reference to the accompanying drawings, in which: Figure la is a sectional view showing a latch device according to the invention, with the door closed; Figure lb is a sectional view taken along line lb-lb in Figure la; Figure lc is a sectional view taken along line lc-lc in Figure la; Figure 2a is a sectional view showing the latch device of Figure la, with the door pushed inward from the normal closed position; Figure 2b is a sectional view taken along line 2b-2b in Figure 2a; Figure 2c is a sectional view taken along line 2c-2c in Figure 2a; Figure 3a is a sectional view showing the latch device shown in Figure la when the door is opened; ; Figure 3b is a sectional view taken along line 3b-3b in Figure 3a; Figure 3c is a sectional view taken along line 3c-3c in Figure 3a; and Figure 4 is a fragmentary perspective view showing the latch device shown in Figure la.

Figures la to lc are sectional views showing a latch device according to the invention, with a door 1 closed. The door 1 is hinged to a body 2 by a hinge (not shown) mounted on one of its edges. The door 1 has a plate-like magnetic substance 3 secured as a striker on its side nearer the body 2. A casing 4 constituting a latch is secured to the body 2 by means of locking pieces 5 formed on its opposite sides and elastically engaging with the edges of a mounting hole 6 formed in the body 2.

In the casing 4, a magnet unit 7 and a slider 8 are provided side by side so that they can be projected and retracted independently. The magnet unit 7 consists of a magnet 9, a pair of plate-like yokes 11 disposed so as to clamp the magnet 9 and a magnet holder 12 of a synthetic resin for holding these members integrally with one another. The magnet holder 12 is guided by the casing 4 so that it can be projected and retracted, and it is spring-biased by a coil spring 13 provided between the bottom wall of the casing 4 and the magnet holder 12 in the direction causing it to project out of the casing 4.

The amount of projection of the magnet unit 7 is restricted by a frame portion 12' at the lower portion of the magnet holder 12 and a stopper projection 4' formed on the inner side of the casing 4. In this way, the magnetic substance 3 of the door 1 is magnetically coupled to the yokes 11 of the projected magnet unit 7, thus holding the door 1 closed.

The slider 8 is a one-piece plastic molding. It is guided so that it can be projected from and retracted into the casing 4 and, like the magnet unit 7, is springbiased by a coil spring 14 provided between the bottom wall of the casing 4 and the lower portion of the slider 8 so that it projects out of the casing 4. The slider 8 has a pair of legs 15 depending from it, and one of its end surfaces is formed with an integral engagement portion 16 extending toward the wall of the casing 4.

The wall of the casing 4 has an opening 17. The engagement portion 16 can enter the opening 17 and is movable vertically in the Figures. The extent of projection of the head of the slider 8 is limited by the engagement of the engagement portion 16 with the upper edge of the opening 17 when the slider 8 is projected.

The magnet unit 7 and slider 8 are adapted to be projected to substantially the same extent. However, the force of projection of the coil spring 14 is greater than the magnetic force of coupling between the magnet 9 and the magnetic substance 3.

In a side portion of the casing 4, as shown in Figure 4, first and second levers 21 and 22 formed integrally via a shaft 23 are supported such that they can be tilted with respect to the side wall of the magnet unit 7 and slider 8. The coil spring 14 has an end 25 extending toward and engaging with an arm 24 so that the two levers 21 and 22 are elastically tilted toward the magnet unit 7 and slider 8. As shown in Figure 2c, the free end of the first lever 21, which is spring-biased toward the magnet holder 12 so as to hold the magnet unit 7 in a retracted position, has a claw-shaped engagement pawl 26 extending toward the magnet unit 7 and capable of engaging with an engagement hole 27. In this way, a movable locking means is formed.

The lower end of one of the legs 15 of the slider 8 is formed with an engagement projection 29. As shown in Figure Ib, the free end of the second lever 22 is formed with a curvedly projecting engagement portion 28, and the leg 15 is formed with a notch 30 so arranged that the engagement portion 28 will not engage with the engagement projection 29 unless the slider is projected.

Thus, when the engagement projection 29 and engagement portion 28 engage with each other, the second lever 22 is tilted in the direction of arrow "A" in Figure lb, and the integral first lever 21 is similarly tilted in the direction of "A" of Figure lc to release engagement between the engagement hole 27 and the engagement pawl 26. In this way, a releasing means is constituted.

Now, the operation of the embodiment of the invention will be described.

Figures la to lc show the device with the door closed. In this state, the yokes 11 of the magnet unit 7 and magnetic substance 3 are magnetically coupled to each other, thus holding the door 1 closed. The magnet unit 7 and slider 8 are both in a projected state, and the engagement projection 29 of the leg 15 of the slider 8 and engagement portion 28 of the second lever 22 are in engagement with each other.

When the door 1 is pushed in the closing direction, the magnet unit 7 and slider 8 retract into the casing 4. At this time, the engagement between the engagement portion 28 and the engagement projection 29 is released, thus permitting elastic tilting of the two levers 21 and 22 in the direction of arrow B in Figures 2b and 2c. Thus, when the magnet unit 7 has completely retracted into the casing 4, the pawl 26 of the first lever 21 projects into the engagement hole 27 of the magnet holder 12, thus causing engagement of the pawl 26 in the hole 27 and holding the magnet unit 7 in a retracted state.

When the force against the door 1 is released, the slider 8, which is elastically biased by the coil spring 14, is projected with a force acting against the magnetic coupling force between the yokes 11 and the magnetic substance 3. Until the slider 8 has projected more than a predetermined extent as shown in Figures 3a to 3c, the magnet unit 7 is held in the retracted state by the first lever 21. The door 1 thus is pushed back by the elastic projecting force of the slider 8 to the state shown by phantom lines so as to cut magnetic flux produced between the yokes 11 and the magnetic substance 3 by the magnet 9, so that it can be readily opened.

When the slider 8 has projected fully from the state shown in Figures 3a to 3c, the engagement projection 29 and engagement portion 28 engage with each other again to cause tilting of the second lever 22 in the direction of arrow "A" in Figure 3b and also tilting of the first lever 21 in the direction of arrow "A" in Figure 3c, thus releasing the engagement between the pawl 26 and the hole 27. Thus, the magnet unit 7 can be projected to obtain the state shown in Figures la to lc.

Thus, since the magnet unit 7 is in a projected state, when the door 1 is to be closed again, it can be held in a closed state by merely bringing the magnetic substance 3 into contact with the yokes 11, and no operation of forcefully pushing the door 1 is needed.

As has been described in the foregoing, according to the invention, during closing of the door it can be held closed by merely causing engagement between the magnetic substance and the magnet means. Thus, even when a deviation is produced in the relative engagement positions of the magnet means and magnetic substance because play developing in the door hinge(s), it is possible to readily obtain engagement of the two with each other. In addition, there is no need of forcefully pushing the door, so that the operation of closing the door can be facilitated. Further, while the magnet means and slider are temporarily retracted by pushing the door in the closing direction when opening the door, the magnet means is held in the retracted state until the projection of the slider is completed. Thus, the door can be smoothly opened by the projecting force of the slider. The operation of opening and closing the door thus can be facilitated, which is very useful.

Claims (3)

1. A latch device, for use with a door mcvable relatively to a body, comprising a magnetic substance secured to one of said door and said body, magnet means received by a casing secured to the other one of said door and said body so that it can project from and retract towards said casing, be spring-biased in the projecting direction and be magnetically coupled to said magnetic substance, a slider received in a juxtaposed relation to said magnet means by said casing so that it can project from and retract towards said casing and be spring-biased with a projecting force greater than the magnetic coupling force between said magnetic substance and said magnet means, movable engagement means spring-biased to hold said magnet means in a retracted position, and releasing means for releasing the state in which said magnet means is held b said movable engagement means when said slider projects more than a predetermined extent.

2. A latch device according te claim 1, in which said slider is continuously biased in the projecting direction by a helical compression spring, one end of which engages an arm projecting from a pivotally mounted shaft from which a pair of levers also project, one of the levers forming part of said movable spring-biased engagement means and having an engagement pawl for engagement with an engagement hole formed in said magnet means, and the other of the levers forming part of said releasing means and having an engagement portion for engagement with an engagement projection projecting from said slider.

3. A latch device substantially as hereinbefore described with reference to the accompanying drawings.