Field of the Invention

The invention relates to an apparatus and method for controlling or affecting the movement of a movable component, and more specifically to an apparatus and method for latching a movable component to another component, and even more particularly to an apparatus and method for latching a movable component to another component in a manner to prevent unlatching by the application of an short duration force to the two components. The invention also relates to an apparatus and method for sensing a stimulus.

Background of the Invention

Latches and locks have long been used in a variety of applications ranging from doors, windows, desk drawers, and so on. Magnetic latches and locks have been used within safety and security doors, disk drive head assemblies, and other applications. One advantage of using a magnetic latch or lock is often the simplification ofthe mechanism because more complex mechanical and/or electrical schemes need not be employed.

U S. Patent No. 5,362, 116 describes a self-latching mechanism for a pool door assembly in which upon exertion of small external force the door is latched to a post segment. The magnetic field applies the needed force to close the door.

U. S Patent No. 5,289,914 describes a magnetic latch and lock as a safety device which provides a locking mechanism for a cassette or a cartridge which can contain a compact disc or a tape. This safety device is mounted on the outside of the cassette to prevent opening and includes a lock member for locking engagement with the cassette The locking member includes a rotary bolt enclosed in a lock housing which is movable between an engaged position and a disengaged position from the outside ofthe lock housing.

U. S. Patent No. 5,381,290 discloses a static bi-stable mechanical latch member which is pivotally mounted to a disk drive frame and is rotatable between an opened-position and a closed-position stop. The latch member includes a first arm and a second arm radially extending from its pivot point. The first arm includes a hooked end which faces the actuator and a soft magnetic material such as an iron mass The iron mass is described as preferably being a small steel ball. The second arm includes a latch coil or magnet mounted thereon and/or a soft magnetic mass such as a small steel ball. The first and second arms comprise an actuator which holds the reading head mechanism for the disk drive. This actuator needs to be parked in order to prevent damage to the head assembly when the disk drive is being moved.

U. S. Patent No. 5,388,437 provides yet another example of a magnetic latch In this case a slide member carries a plurality of wheels in which magnetic pins are mounted. The wheels rotated by insertion of a code changing key, which has a code for unlocking the lock and moving the slide member.

These patents all describe various types of latching mechanisms in which magnetic force causes the engagement and disengagement of two components. However, these mechanisms can be defeated in one way or another. And, many mechanisms can be vulnerable to unlatching by the application of a impact or a short duration force, such as when the mechanism is dropped from a distance onto a hard floor, or when a person purposely strikes the mechanism to defeat the latch.

A need exists for a latching and/or locking mechanism which is not easily unlatched, especially not easily unlatched inadvertently. An apparatus and/or method which satisfies this need could be useful for protecting children and adults from gaining access to dangerous chemicals or medications.

Summary of he Invention

The present invention satisfies this need by providing an apparatus for latching a first component to a second component. The present invention also can be useful in applications other than for latching.

One embodiment ofthe present invention includes an apparatus useful for latching a first component to a second component. The apparatus being useful within an environment where an unlatching force can be applied to the apparatus. The apparatus includes a first latching member operatively coupled to the first component The first latching member is movable between a first latching position and a second latching position. A second latching member is operatively coupled to the second component. The first latching member latches the first and second components when the first latching member is in the first latching position and unlatches the first and second components when in the second latching position. The apparatus further includes deflectable resisting means positioned adjacent to the first latching member for resisting movement ofthe first latching member toward the second latching position by resisting deflection. The deflectable resisting means resists deflection with a resistance force which varies relative to the rate at which the resisting means is deflected. Another embodiment ofthe present invention includes an apparatus useful for preventing the closure of an electrical circuit by an undesirable force. The electrical circuit has first and second electrical contacts. The first electrical contact being movable between a first contact position and a second contact position relative to the second contact. The electrical circuit is open when the first contact is in the first contact position and closed when the first contact is in the second contact position. The apparatus includes deflectable resisting means positioned adjacent to the first electrical contact for resisting movement ofthe first electrical contact toward the second contact position by resisting deflection. The deflectable resisting means resists deflection with a resisting force which varies relative to the rate at which the resisting means is deflected.

Another embodiment ofthe present invention includes an apparatus for indicating when a first component is an indicating distance from a second component. The apparatus includes deflectable resisting means positioned relative to the first and second components for resisting the first component from being the indicating distance from the second component by resisting deflection. The deflectable resisting means resists deflection with a resisting force which varies

relative to the rate at which the resisting means is deflected. The apparatus also includes means for indicating when the first component is the indicating distance relative to the second component.

Another embodiment ofthe present invention includes a method useful for latching a first component to a second component, the method being useful within an environment where an unlatching force can be applied to at least one ofthe first and second components, the first component being operatively coupled to a first latching member. The first latching member is movable between a first latching position and a second latching position. The second component is operatively coupled to a second latching member. The first latching member latches the first component to the second component when the first latching member is in the first latching position and unlatches the first and second components when in the second latching position. The method includes the step of positioning a deflectable resisting member relative to the first component for resisting movement ofthe first latching member toward the second latching position by resisting deflection. The resisting means resists deflection with a resisting force which varies relative to the rate at which the resisting means is deflected.

Another embodiment ofthe present invention includes a method useful for preventing the closure of an electrical circuit by an undesirable force, the electrical circuit having first and second electrical contacts. The first electrical contact are movable between a first contact position and a second contact position relative to the second contact. The electrical circuit is open when the first contact is in the first contact position and closed when the first contact is in the second contact position. The method includes the step of positioning a deflectable resisting means relative to the first and second electrical contacts for resisting movement ofthe first electrical contact toward the second contact position by resisting deflection. The deflectable resisting means resists deflection with a resisting force which varies relative to the rate at which the resisting means is deflected.

Another embodiment ofthe present invention includes a method for indicating when a first component is an indicating distance from a second component. The method includes the step of positioning a deflectable resisting

means relative to the first and second components for resisting the first component from being at the indicating distance from the second component by resisting deflection The deflectable resisting means resists deflection with a resisting force which varies relative to the rate at which the resisting means is deflected. Another step is indicating when the first component is at the indicating distance relative to the second component.

Brief Description of the Drawings

The foregoing advantages, construction, and operation ofthe present invention will become more readily apparent from the following description and accompanying drawings in which:

Figure 1 is a top sectional schematic view of an apparatus in a latched position according to the present invention;

Figure 2 is a top sectional schematic view ofthe apparatus shown in Figure 1 , but the apparatus is shown as being subjected to a compressive force to allow for unlatching;

Figure 3 is a top sectional schematic view ofthe apparatus shown in Figures 1 and 2, but the apparatus is in an unlatched and separated position;

Figure 4 is a top sectional schematic view of another embodiment ofthe apparatus shown in Figures 1-3;

Figure 5 is a top cut-away schematic view ofthe apparatus shown in Figures 1 -3 or Figure 4 within a radiographic imaging cassette;

Figure 6 is a front view of another embodiment ofthe present invention including a cut-away view of a threaded cap; Figure 7 is an enlarged isometric cut-away view ofthe threaded cap shown in Figure 5;

Figure 8 is an enlarged isometric cut-away view of a threaded neck within the embodiment shown in Figures 6 and 7;

Figure 9 is a partial isometric view of a latching mechanism within in the embodiment shown in Figures 6-8;

Figure 10 is a first partial schematic isometric cut-away view of another embodiment ofthe present invention;

Figure 11 is a second partial schematic cut-away isometric view ofthe embodiment shown in Figure 10; and Figure 12 is a cut-away isometric view of another embodiment ofthe present invention.

Detailed Description of Preferred Embodiments

Figures 1-3 collectively illustrate one embodiment of an apparatus for latching a radiographic cassette shell 12 to a radiographic cassette tray 14 to form a radiographic imaging cassette 16, which is shown in Figure 5. The radiographic cassette tray 14 can support a radiographic imaging medium 18 (shown in Figure 5) and can be inserted within the radiographic cassette shell 12. The tray 14 can include a tray endcap 20 which is attached to a tray planar member 22 on which the medium 18 is supported. The tray endcap 20 can mate with the cassette shell 12. A cassette seamline 24 is formed where the tray endcap 20 and cassette shell 12 meet. The radiographic cassette 16 can be useful within an environment where an unlatching force can be applied to radiographic cassette 16. Such an environment could be an X-ray lab in a hospital where several radiographic cassettes are used each day During a given day, a cassette 16 can be dropped from, for example, an X-ray table to the floor. The impact of such a drop can cause the movement of components within the cassette 16.

The apparatus 10 includes a movable latching member 26 shown as being operatively coupled to the radiographic cassette shell 12. The movable latching member 26 can be made of a ferrous material or can include a ferrous insert 27. The movable latching member 26 can be moveable between a first latch position (Figures 1 and 2) and a second latch position (Figure 3). The movable latching member 26 is shown as being a strip or reed which is partially constrained at one end, although other modes of movement and other shapes could allow for the same result For example, the movable latching member 26 could be flexible and fixed at the end ofthe movable latching member. Or, rather than pivoting from one end, the

movable latching member 26 could be pinned (not shown) at its center such that it would rotate around the pinned center.

A stationary latching member 28 is shown in Figures 1-3 as being operatively coupled to the radiographic cassette tray 14. The stationary latching member 28 can include a notch wall 30 which is peφendicular to a main wall 32 of the cassette tray 14. The movable latching member 26 latches the radiographic cassette shell 12 to the radiographic cassette tray 14 when the movable latching member 26 is in the first latching position and unlatching the radiographic cassette shell 12 from the radiographic cassette tray 14 when the movable latching member 26 is in the second latching position.

A magnet 34 is shown in Figures 1-3 as being positionable adjacent to the movable latching member 26. Because the movable latching member 26 is made of a ferrous material or includes a ferrous insert 27, the magnet 34 can attract the movable latching member 26 toward the second latching position, as shown in Figure 3.

To accomplish a similar result, the movable latching member 26 could include an embedded magnet. With the configuration, the magnet 34 and the embedded magnet could be oriented to attract one another to unlatch the apparatus 10 Or, as shown in Figure 4, the magnet 34 and the embedded magnet 35 could be oriented to repel one another to unlatch the apparatus 10. (In Figure 4, the unlatching direction ofthe movable latching component 26 is opposite to that shown in Figures 1-3.)

To accomplish a similar result in still another way, the movable latching member 26 could be magnetic and the magnet 34 could be replaced by an object (not shown) made of ferrous material. In any of these embodiments, to move the movable latching member 26 from the first latching position to the second latching position, the ferrous insert 27 (or the first magnetic material) must be sufficiently close proximity to the magnetic material (or the second magnetic material) and the magnetism must be of sufficient strength. A first resilient foam member 36 is shown as being operatively coupled to the movable latching member 26. The first resilient foam member 36 can bias the

movable latching member 26 toward the first latch position and resist movement of the movable latching member 26 toward the second latch position. The first resilient member could be thought of as a deflectable resisting means.

The first resilient foam member 36 can have a spring constant which varies relative to the rate at which the first resilient foam member 36 is strained. In other words, when the resilient foam member 36 must be compressed for the movable latching member 26 to move to the second latching position, the spring constant k ofthe foam member 36 varies based upon to the rate (dX/dt) at which the foam member 36 is being compressed due to the compressive force. Consequently, for a given compressive force, the spring force F resisting compression (based on the equation: F = k X) will increase as the rate of compression dX/dt increases. Conversely, for a given compressive force, the spring force F resisting compression will decrease as the rate of compression dX/dt decreases. (The foam member 36 performs similarly when the apparatus 10 is configured to perform by stretching the resilient foam member 36 (tension mode) to allow the movable latching member 26 to move to the second latching.)

The variable spring constant ofthe resilient foam member 36 can be chosen such that a resilient foam member 36 will apply a sufficiently large spring force F to prevent the movable latching member 26 from moving to the second latch position due to the application of a given unlatching force which results in a relatively high compression rate ofthe resilient foam member 36. Examples of such unlatching forces include the impact from an inadvertent drop and the impact from an intentional strike by a person in an attempt to defeat the latch.

When the apparatus 10 is configured such that the operative end ofthe movable latching member 26 need only move a distance slightly greater than the thickness ofthe movable latching member 26 (e.g., 0.05 inch (0.127 centimeter)), the first resilient foam member 36 can be configured to prevent unlatching by the application of a relatively large unlatching force F for a duration of approximately 0.01 second, 0.02 second, 0.05 second, 0.10 second, or an even longer duration. A relatively large unlatching force can occur when the apparatus 10 is a part of a device, such as a radiographic cassette, which is dropped on an edge or corner such

that movable latching member 26 is forced toward the second latching position. Preferably, the movable latching member 26 is of low mass such that force applied by the movable latching member 26 to the resilient foam member 38, during such an impact, is minimized and unlatching is prevented. The preferred low mass is achievable in that the movable latching member 26 need not be made to withstand severe stress due to an impact. This is because the apparatus 10 is configured such that the movable latching member 26 is not compressed when the cassette 16 is impacted in any direction.

Conversely, when the deflection (compression or tension) rate is low, such as that induced by a relatively small magnetic attraction, the first resilient foam member 36 reacts with a lower spring constant than if the rate of deflection were high like, for instance, that ofthe previously described impact examples.

One example of a suitable foam for the first resilient foam member 36 is Isoloss Confor foam CF-40025, which is made by E-A-R Specialty Composites Division, Cabot Safety Coφoration (7911 Zionsville Road, Indianapolis, Indiana 46268). Other versions of this foam and other foams can be chosen to suit the use ofthe apparatus 10.

Any material whose compressive and tensile modulus is dependent on strain rate could function in place ofthe foam. An example could be a coil spring or a leaf spring made of such a strain rate dependent material. Another example is an oil shock-absorbing device. Foam, however, can be a good choice for applications which involve minimal compression force. Foam is relatively cost-effective and, with the use of adhesive, is relatively easily positioned and fixed within the apparatus 10. Other means of moving the movable latching member 26 are also envisioned. A key could be fashioned to slide along the movable latching member deflecting it away from the stationary latching member. The movable latching member could be bi-metallic such that heat could be applied to it which would cause the movable latching member to deflect due to the differential thermal expansion ofthe metals (thermal moving means). The movable latching member could be composed of or actuated by a shape memory alloy which would move or

change length when a current is applied to the alloy (electrical moving means). Still other moving means are apparent, such as air flow against the movable latching member 26 (pneumatic moving means) or a mechanism including a small motor (mechanical moving means). As shown, the apparatus 10 can further include a second resilient foam member 38 which can be coupled to, for example, the tray endcap 20 (or to an outer wall at the opening ofthe cassette shell 12). The second resilient foam member 38 can provide a fluid seal at the cassette seamline 24 to prevent or, at least, minimize the flow of fluids into the cassette shell 12 when the cassette shell 12 and the cassette tray 14 are joined.

As illustrated in Figure 1, the second resilient foam member 38 can provide another advantage by biasing the movable latching member 26 toward the stationary latching member 28 which can create sufficient friction between the movable and stationary latching members 26, 28 to prevent the movable latching member 26 from moving from the first latch position to the second latch position. This is the case even when the magnet 34 is within a sufficiently close proximity to the ferrous insert 27 to apply a moving force to overcome the biasing ofthe first resilient foam member 36. In effect, the second resilient foam member 38 is a means for engaging the first and second latching members 26, 28. Even when the cassette 16 is dropped such that the second resilient member

38 is compressed and the movable latching member 26 is disengaged from the stationary latching member 28, the latching apparatus 10 can prevent unlatching. When the cassette 16 is dropped, the first resilient member 36 resists the movement ofthe movable latching member from the first latching member due to the previously described high-strain-rate feature provided by the first resilient member 36.

So, to unlatch the cassette tray 14 and the cassette shell 12, a force P can be applied, as shown in Figure 2, which moves the cassette shell 12 and cassette tray 14 closer together which eliminates the friction between the movable latching member 26 and the stationary latching member 28. While the friction can be sufficient to function as described, the stationary latching member 28 could further

include a lip (not shown) which holds the movable latching member 26 in the first latching position until the previously described push-pull movement and magnetic attraction occurs. And, another form of biasing means in place ofthe second resilient foam member 38 could be used. However, the fluid barrier feature provided by the second resilient foam member 38, if desired, may require the inclusion of another component.

The biasing feature provided by the second resilient foam member 38, which creates the need for the push-pull movement to unlatch the cassette shell 12 and the cassette tray 14, can be useful in several situations. One such situation is when the ferrous insert 27 is exposed to a magnetic field which is not intended for the puφose of unlatching the cassette shell 12 and the cassette tray 14. For example, a magnetic field created by magnetic resonance imager (MRI) could apply such a field to the ferrous insert 27. In addition to this, the first resilient foam member 36 can be configured to require that a magnetic field be applied to the ferrous insert 27 for a certain period of time to prevent unlatching by the inadvertent, short durational application of a magnetic field to the ferrous insert 27.

Figure 5 more generally illustrates the radiographic cassette 16 (partially opened) and the magnet 34. The magnet 34 could be connected to a mechanism within a device (not shown) which manipulates the radiographic cassette 16 and extracts or reads the image stored in the radiographic imaging medium 18. When the cassette 16 is placed or transported, for example, to within the image reading extracting device, the mechanism could bring the magnet 34 to the correct position to apply the magnetic field to the apparatus 10 to unlatch the cassette tray 14 and the cassette shell 12. The cassette 16 could include two (or more) latching apparatuses 10, one on each side as shown in Figure 5, such that the image reading/extracting device would require two magnets 34 and two mechanisms. Plus, if the second resilient foam member 38 is employed within the cassette 16 to bias the movable and stationary latching members 26, 28 together, another mechanism within the image reading/extracting device would be needed to apply the compressive force to allow the magnetic field to move the movable latching member 26 to the second latching position.

Figure 5 also illustrates that the apparatus 10 can be concealed. That is, a user may not even be aware ofthe apparatus 10 because the apparatus 10 is largely hidden or concealed within the cassette shell 12. Because a reading/extracting device may used to open and close the cassette 16 and because the radiographic imaging medium 18 can capture a radiographic image while the cassette shell 12 and cassette tray 14 are joined, there is not need for a user to know how to separate the cassette shell 12 and the cassette tray 14. The ability to operate while being concealed can be useful in a variety of latching applications.

Other latching embodiments are contemplated such as for latching a video cassette or other cassettes or pairs of components which are movable relative to each other. For example, Figures 6-9 illustrate a latching embodiment in which the apparatus 10A as part of a container 40A and a threaded cap 42 A. Containers which would particularly benefit by the inclusion ofthe apparatus 10A are medication containers which could fall into the hands of a child, and chemical containers which are preferably openable only when intended. In Figures 6 and 7, a portion ofthe cap 42 A is cut away to show the general position ofthe apparatus 1 OA within the cap 42A and the neck 44A ofthe container 40A. In Figure 8, the neck 4 A is shown as having a neck notch 46A. In Figure 9, the apparatus 10A is shown in more detail and illustrates how the apparatus 10A latches the cap 42 A to the neck 44A when the cap 42A is screwed down onto the neck 44A.

Similar to the embodiment ofthe apparatus 10 shown in Figures 1-5, movable and stationary latching members are involved. The stationary latching member is the neck notch 46A specifically shown in Figure 8, and the movable latching member is a cap arm 48A extending from the interior ofthe cap 42A. The cap arm 48A could be molded as part ofthe cap 42A and have a living hinge 50A for pivoting the arm latching end 52 A in and out ofthe neck notch 46 A, as best shown in Figure 9. To unlatch the arm latching end 52A from the neck notch 46A, the cap 42A would be turned more tightly to disconnect the arm latching end 52A and the cap 42A and the magnet 34A could be in sufficiently close proximity to the ferrous insert 27A to pull the arm latching end 52A out ofthe neck notch 46A. At this time, the cap 42A could be screwed off the neck 44A of he container 40A.

The coordination ofthe tighten-untighten movement and the proximity ofthe magnet 34A would be difficult for a young child to comprehend and accomplish, and would be difficult to accomplish unintentionally by an adult.

For convenience, the magnet 34A could be in some way connected to the cap 42A (not shown). Also, this embodiment could include a first resilient member 36A to provide the previously described variable strain rate feature. In addition, the engagement ofthe arm latching end 52A and neck notch 46A is enhanced in that the wall ofthe neck notch 46 A which contacts the arm latching end 52 A is not a vertical wall, but an angling undercut. A similar enhancement could be achieved by having an undercut which is not angling inwardly, but horizontal which disallows vertical movement ofthe arm latching end 52 without the previously described tightening step. (These engaging enhancements could be employed in the previously described embodiments, such as the radiographic cassette embodiment.) Another embodiment ofthe apparatus 10B is shown in Figures 10 and 11 for sensing a stimulus (and/or latching two objects together). This embodiment shows the breadth ofthe present invention and how the present invention can be generally considered an apparatus (and method) for controlling or affecting the movement of a movable component. In this embodiment, a magnet-receiving keyway or opening 54B is shown as having a particular shape. (The opening 54B is cut-away for illustrative puφoses.) The complementary shape and proximity of the magnet 34B is important to unlatching the movable latching member 26B. The field strength of a magnet 34B and, therefore, its attractive (or repulsive) force, falls off rapidly as the distance from the target (e.g., ferrous insert 27B or a magnetic insert) is increased. A powerful magnet 34B that is not relatively close to its attracted target may not have enough field strength to move the target. The apparatus 10 could be configured such that other receiving means, other than the opening 54B shown in Figures 10 and 11, could also be used.

The movable latching member 26B can rotate about a pivot 56B when a sufficiently strong magnetic field is present to attract the ferrous insert 27B. The ferrous insert 27B can be sufficiently small that it would require a powerful magnet 34B with a high field strength to be relatively close before a sufficiently large

attractive (or repulsive) force would be applied to the movable latching member 26B. Since the attractive force depends on the number of flux lines attracting the ferrous insert 27 A, a small magnet 34B with the same field strength as a larger magnet would attract the ferrous insert 27A with the same force as the larger magnet that is same distance from the ferrous insert 27A.

Additionally, a shunt 58B can be added to limit or interrupt the magnetic field created by a large and powerful magnet. The shunt 58B could simply be a ferrous plate or the like which surrounds at least a portion ofthe magnet-receiving opening 54B through which the intended magnet 34B can fit. By interrupting the field of a large and powerful magnet, the shunt 58B reduces the number of magnetic lines the large magnet could bring to bear on the movable latching member 26B. As such, the shunt 58B acts as another level of protection against defeating the apparatus 10B. But, by simply having a shaped opening in the shunt 58B and a magnet 34B with a mating shape that allows a portion ofthe magnet 34B to pass through the shaped opening, the apparatus 10B can be unlatched when desired. The embodiment ofthe apparatus 10B shown in Figures 10 and 11 could include electrical contacts 60B, 62B such that the apparatus 10B would be part of a sensing scheme. The electrical contacts 60B, 62B could be wired to a sensing device (not shown) such that the sensing device would be alerted when the magnet 34B was sufficiently close to the ferrous insert 27B to cause the movable member 26B to move and the electrical contacts 60B, 62B to meet (and close a sensing circuit).

A first resilient foam member 36B could be included to this embodiment, as shown in Figures 10 and 11. The first resilient foam member 36B could prevent the electrical contacts 60B, 62B from meeting if a force is applied instantaneously or for a relatively short duration to one or both ofthe electrical contacts 60B, 62B. Similar to the previously described embodiments, the first resilient foam member 36B could prevent movement of a critical component (e.g., a movable electrical contact 60B) when the apparatus 10B is dropped on the ground and subjected to an instantaneous impact.

Another embodiment ofthe apparatus IOC for sensing a stimulus is shown in Figure 12. In this embodiment, the apparatus IOC could be part of a device (not shown) useful for sensing when the apparatus IOC is subjected to an external pressure. For example, when submersed further and further into a body of liquid (not shown), the apparatus IOC could signal when the apparatus IOC reaches a particular depth and is subjected to pressure created by the column of liquid above the apparatus IOC. To allow for this, the apparatus IOC could be sealed from the external environment and could include an inner chamber 64C. A magnet 34C could be attached to a flexible portion ofthe chamber wall, such as a membrane 66C, such that the external pressure could flex the membrane 66C and the attached magnet 24C into the interior chamber 64C. A ferrous insert 27C which is attached to a movable member 26C could be attracted due to the proximity ofthe magnet 34C and could close a circuit made up partially of electrical contacts 60C, 62C (similar to the electrical contacts 60B, 62B shown in Figures 6 and 7). By closing the circuit, the apparatus IOC would, in effect, send a signal to an indicator (not shown) which could alert a person or a machine to the fact that the apparatus IOC has submersed to a particular depth. Variations on this embodiment can be suitable for sensing stimuli other than external pressure and for a variety of sensing applications other than depth sensing.