Interlock mechanism for lateral file cabinets

Information

  • Patent Grant
  • 6779855
  • Patent Number
    6,779,855
  • Date Filed
    Thursday, February 27, 2003
    21 years ago
  • Date Issued
    Tuesday, August 24, 2004
    20 years ago
Abstract
Interlocks for file cabinets and the like which generally prevent more than one drawer from being opened at a given time. The interlocks include a elongated, flexible member, such as a cable, which is changeable from a high slack condition to a low slack condition. In the low slack condition, the interlocks prevent their associated drawers that are closed from being opened. In the high slack condition, the interlocks allow their associated drawer to be opened. The interlocks may be used in conjunction with a lock that selectively changes the cable from a high slack condition to a low slack condition and vice versa. The interlocks may be constructed to exert a force on the cable that is independent of the pulling force exerted on a locked drawer.
Description




BACKGROUND OF THE INVENTION




The present invention relates to filing cabinets, and more particularly to mechanisms adapted to prevent one or more of the drawers in the filing cabinet from being opened.




It has been known in the past to include interlock mechanisms on filing cabinets that prevent more than one drawer in the cabinet from being opened at a single time. These interlock mechanisms are generally provided as safety features that are intended to prevent the filing cabinet from accidentally falling over, a condition that may be more likely to occur when more than one drawer in the cabinet is open. By being able to open only a single drawer at a given time, the ability to change the weight distribution of the cabinet and its contents is reduced, thereby diminishing the likelihood that the cabinet will fall over.




In addition to such interlocks, past filing cabinets have also included locks that prevent any drawers from being opened when the lock is moved to a locking position. These locks are provided to address security issues, rather than safety issues. These locks override the interlocking system so that if the lock is activated, no drawers may be opened at all. If the lock is not activated, the interlock system functions to prevent more than one drawer from being opened at the same time. Oftentimes the system that locks all of the drawers and the interlock system that locks all but one of the drawers are at least partially combined. The combination of the locking system with the interlocking system can provide cost reductions by utilizing common parts.




Past locking and interlocking mechanisms, however, have suffered from a number of disadvantages. One disadvantage is the difficulty of changing the drawer configurations within a cabinet. Many filing cabinets are designed to allow different numbers of drawers to be housed within the cabinet. For example, in the cabinet depicted in

FIG. 1

, there are three drawers in the cabinet. For some cabinets, it would be possible to replace these three drawers with another number of drawers having the same total height as the three original drawers. This reconfirmation of the drawers is accomplished by removing the drawer slides on each side of the drawer and either repositioning the drawer slides at the newly desired heights, or installing new drawer slides at the new heights. Many drawer slides include bayonet features that allow the drawer slides to be easily removed and repositioned within the cabinet.




In the past, such reconfiguring of the drawers in a cabinet has been a difficult task because the interlocking and/or locking system for the drawers could not easily be adjusted to match the newly configured filing cabinet. For example, U.S. Pat. No. 6,238,024 issued to Sawatzky discloses an interlock system that utilizes a series of rigid rods that are vertically positioned between each drawer in the cabinet. The height of these rods must be chosen to match the vertical spacing between each of the drawers in the system. If the cabinet is to be reconfigured, then new rods will have to be installed that match the height of the new drawers being installed in the cabinet. Not only does this add additional cost to the process of reconfiguring the cabinet, it complicates the reconfiguring process by requiring new parts of precise dimensions to be ordered. Finding these precisely dimensioned parts may involve extensive searching and/or measuring, especially where the manufacturer of the rods is not the same entity that produced the new drawers being installed, or the manufacturer of the rods has ceased producing the parts, or has gone out of business.




Another difficulty with systems like that disclosed in the Sawatzky patent is the precise manufacturing that may be required to create these rigid rods. These interlock systems only work if the rods have heights that fall within a certain tolerance range. This tolerance range, however, decreases as more interlocks are installed in a given cabinet. In other words, the tolerance of the heights of these rods is additive. In order to function properly, a cabinet with ten drawers will therefore require smaller tolerances in the rods than a two drawer cabinet. In order to create rods that can be universally used on different cabinets, it is therefore necessary to manufacture the rods within the tight tolerances required by the cabinet having the greatest expected number of drawers. These tight tolerances tend to increase the cost of the manufacturing process.




Another difficulty with past interlock and lock systems for file cabinets has been the expense involved in creating a locking system that will withstand high forces exerted on the drawers. The Business and Institutional Furniture Manufacturer's Association (BIFMA) recommends that lock systems for file cabinets be able to withstand 50 pounds of pressure on a drawer. Thus, if a file cabinet does not exceed this standard, thieves can gain access to the contents of a lock drawer by pulling the drawer outwardly with more than fifty pounds of force. Many users of file cabinets, however, desire their locking system to be able to withstand much greater forces than this before failure. Increasing the durability of the locking system often adds undesired expense to the cost of building the system.




A number of prior art interlock systems have used cables or straps as part of the interlocking system. Such systems, however, have suffered from other disadvantages. For example, U.S. Pat. No. 5,199,774 issued to Hedinger et al. discloses an interlock and lock system that uses a cable. The slack in the cable is decreased when a drawer is opened. The amount of slack of the cable is carefully chosen during the installation of the drawer lock so that there is just enough in the system to allow only one drawer to be opened at a time. The interlock on whatever drawer is opened takes up this available slack in the cable, which prevents other drawers from being opened at the same time. A similar system is disclosed in U.S. Pat. No. 5,062,678 issued to Westwinkel. This system uses a strap instead of a cable. Both systems suffer from the fact that excessive amounts of force may be easily transferred to either the cable or the strap. In other words, the cable or the strap itself are what resist the pulling force that a person might exert on a closed drawer when either the lock is activated, or another drawer is opened. The tensile strength of the cable or strap therefore determines how much force must be exerted to overcome the interlock or lock. In fact, in the interlock of Westwinkel, the system appears to be constructed so that the pulling force exerted by a person on a locked drawer will be amplified before being applied to the strap. The strap must therefore have a greater tensile strength than the highest rated pulling force that the lock or interlock system can resist. Increasing the strength of the cables or straps typically tends to increase their cost, which is desirably avoided.




In light of the foregoing, the desirability of an interlock and lock system that overcomes these and other disadvantages can be seen.




SUMMARY OF THE INVENTION




Accordingly, the present invention provides an interlock and lock that reduces the aforementioned difficulties, as well as other difficulties. The interlock and lock of the present invention allow relatively low-tensile strength cables or flexible members to be used in systems which provide high resistance to theft and breakdown. The system of the present invention further allows changes to cabinet configurations to be easily implemented with little or no additional work required to integrate the new cabinet configuration into the interlock or lock system. The present invention provides a simple construction for locks and interlocks that can be easily manufactured without excessively restrictive tolerances, and which can be easily installed in cabinets.




According to one aspect of the present invention, an interlock is provided that includes a cable, a slack take-up mechanism, a cam, and a biasing member. The slack take-up mechanism is engageable with the cable and movable between a higher slack position and a lower slack position. The lower slack position causes the cable to exist in a relatively lower slack condition. The higher slack position allows the cable to exist in a relatively higher slack condition. The cam is operatively coupled to the slack take-up mechanism and to the drawer. The cam is adapted to switch the slack take-up mechanism from the higher slack position to the lower slack position when the drawer is moved in the first direction toward the open position. The biasing member is adapted to exert a force against the take-up mechanism that urges the slack take-up mechanism toward the lower slack position. The force of the biasing member may have a magnitude that is independent of the magnitude of the force exerted on the drawer in the first direction.




According to another aspect of the present invention a cabinet is provided. The cabinet includes at least one drawer, a frame, an elongated, flexible member, and an interlock. The interlock is adapted to prevent the drawer from opening when the elongated, flexible member is in the lower slack condition, and to allow the drawer to open when the flexible member is in the higher slack condition. The interlock includes a slack take-up mechanisms that changes the flexible member from the higher slack condition to the lower slack condition when the drawer is opened. The slack take-up mechanism is further adapted to exert a force on the elongated, flexible member that has a magnitude that is independent of a force applied in the first direction to the drawer.




According to still other aspects of the present invention, the interlock may be in communication with a lock that is adapted to selectively alter the condition of the cable. The interlocks may be secured to drawer slides that are removable from the cabinet. A cable guide may be included as part of the interlock to snap-fittingly receive the cable and retain it in engagement with the interlock.




The various aspect of the present invention provides an interlock and lock system that is versatile, resistant to high forces, and easily installed. These and other benefits of the present invention will be apparent to one skilled in the art in light of the following written description when read in conjunction with the accompanying drawings.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a perspective view of a cabinet with three drawers in a closed position;





FIG. 2

is a perspective view of the cabinet of

FIG. 1

illustrated with one drawer moved to an open position;





FIG. 3

is a side, elevational view of an interlock and drawer slide according to a first embodiment of the present invention;





FIG. 4

is a perspective view of a pair of interlocks according to the first embodiment of the present invention;





FIG. 5

is a side, elevational view of the pair of interlocks of

FIG. 4

;





FIG. 6

is a perspective, exploded view of the interlock of

FIG. 3

;





FIG. 7

is a perspective view of the interlock of

FIG. 3

illustrated without a drawer slide attached;





FIG. 8

is a perspective view of an attachment plate of the interlock of

FIG. 3

;





FIG. 9

is a plan view the attachment plate of

FIG. 8

;





FIG. 10

is a side, elevational view of the attachment plate of

FIG. 8

;





FIG. 11

is a perspective view of a sliding plate of the interlock of

FIG. 3

;





FIG. 12

is a plan view of the sliding plate of

FIG. 11

;





FIG. 13

is a side, elevational view of the sliding plate of

FIG. 11

;





FIG. 14

is a perspective view of a cam of the interlock of

FIG. 3

;





FIG. 15

is a plan view of the cam of

FIG. 14

;





FIG. 16

is a side, elevational view of the cam of

FIG. 14

;





FIG. 17

is a perspective view of an engagement member of the interlock of

FIG. 3

;





FIG. 18

is a front, elevational view of the engagement member of

FIG. 17

;





FIG. 19

is a perspective view of a rivet of the interlock of

FIG. 3

;





FIG. 20

is a side, elevational view of a spring of the interlock of

FIG. 3

;





FIG. 21

is a perspective view of a cable guide of the interlock of

FIG. 3

;





FIG. 22

is a bottom view of the cable guide of

FIG. 21

;





FIG. 23

is a plan view of the cable guide of

FIG. 21

;





FIG. 24

is a side, elevational view of the interlock and drawer slide of

FIG. 3

illustrated with the interlock in a locked position;





FIG. 25

is a side, elevational view of the drawer slide and interlock of

FIG. 3

illustrating the interlock in a position in which two drawers are being simultaneously pulled toward an open position;





FIG. 26

is a side, elevational view of the drawer slide and interlock of

FIG. 3

illustrating the interlock in an open position with the drawer slide contacting the cam;





FIG. 27

is a side, elevational view of the drawer slide and interlock of

FIG. 3

illustrating the interlock in an unlocked position, and the drawer slide disengaged from the cam;





FIG. 28

is a perspective view of a lock illustrated in a locked position;





FIG. 29

is a side, elevational view of the lock of

FIG. 28

in the locked position;





FIG. 30

is a perspective view of the lock of

FIG. 28

illustrated in an unlocked position;





FIG. 31

is a side, elevational view of the lock of

FIG. 30

in the unlocked position; and





FIG. 32

is a perspective, exploded view of the lock of FIG.


28


.











DETAILED DESCRIPTION OF THE INVENTION




The present invention will now be described with reference to the accompanying drawings wherein the reference numerals in the following written description correspond to like numbered elements in the several drawings. The present invention relates to locks and interlocks that may be used with file cabinets, such as the file cabinet


60


depicted in

FIGS. 1 and 2

. File cabinet


60


includes three drawers


62




a-c


that are essentially stacked on top of each other in file cabinet


60


. Each drawer can be pulled in a first direction


64


toward an open position. The lower most drawer


62


c in

FIG. 2

is illustrated in the open position. When it is time to close this drawer, it can be pushed in a second direction


66


back to its closed position. The interlocking system of the present invention prevents more than one drawer from being opened at a single time. While only three drawers are illustrated in file cabinet


60


, the present invention is applicable to cabinets having any number of drawers. The present invention also includes a locking system that overrides the interlocking system. That is, when the locking system is activated, no drawers can be opened at any time. When the locking system is deactivated, the interlocking system is activated and prevents more than one drawer from being opened at a single time. The locking system may be activated by inserting a key into a keyhole


68


positioned at any suitable location on the file cabinet. The locking and interlocking system are highly integrated so that many of the components of the interlocking system are also used in the locking system.




The interlocks of the present invention may be advantageously combined or attached to the drawer slides in which drawers


62


slidingly move between their open and closed position. An example of one of these drawer slides


70


is depicted in

FIG. 2

for the lower most drawer


62




c


. Each drawer


62


includes two drawer slides


70


, one positioned on one side of the drawer and another positioned on the opposite side of the drawer. While the interlocks of the present invention can be placed at other locations besides on drawer slide


70


, the attachment of the interlocks to the drawer slide


70


allows the interlocks to be simultaneously removed and repositioned when the drawer slides


70


are removed and repositioned. This greatly facilitates the reconfirmation of a file cabinet


60


with differently sized drawers


62


.




An interlock


72


according to a first embodiment of the present invention is depicted in FIG.


3


. Interlock


72


is attached to a drawer slide


70


. Interlock


72


is operatively coupled to a cable


74


that runs vertically inside of cabinet


60


. In general, interlock


72


operates according to the amount of slack in cable


74


. Specifically, cable


74


has two different basic levels of slack. When no drawers are opened and the lock is not activated, cable


74


has a high amount of slack in it. When a single drawer is opened, interlock


72


takes up most or all of the slack in cable


74


and creates a second, lower level of slack in cable


74


. The lower level of slack in cable


74


is such that no other drawers in the cabinet


60


can be opened. This lower level of slack may be zero, or may include a small amount of slack. When the open drawer is closed, more slack in the cable


74


returns and any other single drawer may thereafter be opened. If a lock is included with the cabinet


60


, the lock is adapted to alter the slack in cable


74


. When in the locked position, the lock removes most or all of the slack in cable


74


. When in the unlocked condition, the lock allows cable


74


to have sufficient slack so that a single drawer may be opened. Interlocks


72


are thus designed to only allow their associated or attached drawer to be opened when cable


74


has sufficient slack. Further, they are designed to remove substantially all of the slack in cable


74


, if their associated drawer is opened. The detailed construction of interlock


72


, as well as how they accomplish the aforementioned functions, will now be described.




As illustrated in

FIG. 6

, interlock


72


generally includes an attachment plate


76


, a sliding plate


78


, a rotatable cam or lever


80


, a spring


82


, a cable guide


84


, an engagement member


86


, and a rivet


88


. Attachment plate


76


is a stationary part that secures interlock


72


to drawer slide


70


. Specifically, attachment plate


76


is secured to a stationary portion


90


of drawer slide


70


. Stationary portion


90


is illustrated in

FIGS. 4 and 5

. Stationary portion


90


is, in turn, secured to appropriate attachment structures within file cabinet


60


. Those attachment structures may allow drawer slide


70


to be easily removed and repositioned inside of cabinet


60


. Attachment plate


76


may be secured to stationary portion


90


of drawer slide


70


in any suitable fashion, such as by welding, or the use of fasteners.




Attachment plate


76


includes a plurality of fastener holes


92


which may be used to receive rivets, screws, or other fasteners to secure attachment plate


76


to stationary portion


90


of drawer slide


70


. Attachment plate


76


is depicted in detail in FIGS.


6


and


8


-


10


. Attachment plate


76


further includes a rivet hole


94


which receives rivet


88


. Rivet


88


secures cam


80


to attachment plate


76


in a rotatable fashion. Stated alternatively, cam


80


is attached to attachment plate


76


in such a manner that it can rotate about the axis generally defined by rivet


88


. Attachment plate


76


further includes a spring attachment nub


96


to which one end of spring


82


is attached. Attachment plate


76


also includes a pair of bent flanges


98


. Bent flanges


98


are received inside of cable guide


84


and used to secure cable guide


84


to attachment plate


76


. Each flange


98


includes a shoulder


100


that retains cable guide


84


on attachment plate


76


after they have been attached, as will be explained in more detail below.




Sliding plate


78


, which is depicted in detail in FIGS.


6


and


11


-


13


, is positioned between attachment plate


76


and cam


80


. Sliding plate


78


slides linearly in a direction parallel to first and second directions


64


and


66


. When a drawer


62


is initially opened, sliding plate


78


slides linearly in first direction


64


. As the drawer fully closes, sliding plate


78


slides back to its original position in second direction


66


. Sliding plate


78


includes an elongated aperture


102


that receives rivet


88


. Because elongated aperture


102


has a length much greater than the diameter of rivet


88


, sliding plate


78


can slide along rivet


88


while still being supported by rivet


88


. Sliding plate


78


includes an engagement lug


104


positioned at an end generally opposite to elongated aperture


102


. Engagement lug


104


engages cable


74


generally along its side that faces toward elongated aperture


102


. The side of sliding plate


78


adjacent engagement lug


104


is supported in a channel


106


defined by cable guide


84


. When sliding plate


78


slides in first direction


64


, engagement lug


104


, which is in engagement with cable


74


, decreases the slack in cable


74


. Thus, when a drawer is open, sliding plate


78


and engagement lug


104


remove most or all of the slack from cable


74


. This will be described in more detail below.




Sliding plate


78


further includes a spring attachment nub


108


. Spring attachment nub


108


is used to attach the other end of spring


82


to sliding plate


78


. When spring


82


is connected between attachment nubs


108


and


96


, spring


82


exerts a force that tends to urge attachment nubs


96


and


108


toward each other in a direction generally parallel to first direction


64


. The movement of sliding plate


78


toward spring attachment nub


96


of attachment plate


76


is limited by an interior surface


110


of elongated aperture


102


. When interior surface


110


contacts rivet


88


, sliding plate


78


can no longer be moved any further in first direction


64


. As will be described in more detail herein, spring


82


exerts the slack-removal force on cable


74


, by way of engagement lug


104


when a drawer is opened. Depending on the physical construction of interlock


72


, as well as the type of cable


74


chosen, spring


82


may be desirably chosen to exert a force against sliding plate


78


of one to two pounds in a first direction


64


when a drawer is open. Other amounts of force can also be used within the scope of the present invention. The amount of this force should be sufficient to overcome the cumulative friction between the cable and all of the parts it is in contact within interlock


72


, as well as the other interlocks within the cabinet. Stated alternatively, spring


82


should be sufficiently strong to remove or reduce the slack in cable


82


by pulling sliding plate


78


sufficiently far in first direction


64


to allow an embossment


112


, described below, to fit into a channel


120


on cam


80


. Once positioned therein, a surface


121


in channel


130


prevents sliding plate


78


from retreating in second direction


66


until the drawer is closed. This retains cable


74


in a low slack condition whenever any other drawers are attempted to be opened.




As mentioned, sliding plate


78


further includes an embossment


112


on a side


114


that faces cam


80


. Embossment


112


is positioned between elongated aperture


102


and engagement lug


104


. Embossment


112


interacts with cam


80


in a manner that will be described in more detail herein. In general, cam


80


acts as a switch for moving sliding plate


78


between a slack-removal position, in which a force is exerted on cable


74


, and a slack position, in which no force is exerted on cable


74


. This switching occurs when the drawer associated with interlock


72


is opened or closed. This switching utilizes embossment


112


, as explained more below.




Cam


80


, which is depicted in more detail in FIGS.


6


and


14


-


16


, includes a central aperture


116


which receives rivet


88


. As mentioned previously, cam


88


is rotatable about rivet


88


. Cam


80


includes a pair of spaced flanges


118


that define a channel


120


therebetween. Channel


120


selectively receives engagement member


86


. Engagement member


86


is attached to the drawer


62


such that it will move linearly in first direction


64


when the drawer is open, and in second direction


66


when the drawer is closed. Cam


80


translates this linear motion into a rotational motion. Cam


80


includes a first surface


122


that engages embossment


112


whenever the associated drawer is fully closed. Raised shoulders


124




a


and


b


are defined adjacent each end of first surface


122


. Raised shoulders


124




a


and


b


tend to maintain embossment


112


on first surface


112


and thereby resist inadvertent rotation of cam


80


.




From the position illustrated in

FIG. 6

, cam


80


is generally rotatable in a direction


126


. This rotation in direction


126


is activated by the associated drawer being pulled toward the open position. When the drawer is so pulled, engagement member


86


begins to move in first direction


64


. Because engagement member


86


is housed within channel


120


, this movement in first direction


64


causes cam


80


to begin to rotate in direction


126


. As this rotation continues, raised shoulder


124




a


of cam


80


comes into contact with embossment


112


. In order for the rotation of cam


80


to continue, sliding plate


78


must be pushed in second direction


66


a small amount in order to provide clearance for embossment


112


to overcome shoulder


124




a


. Shoulder


124




a


is an optional feature that, if provided, helps to ensure that the drawer stays shut after it is closed. If the drawer is shut hard enough to create a rebounding force that would otherwise cause the drawer to open back up again, at least partially, shoulder


124




a


provides sufficient resistance to generally prevent this rebounding force to open the drawer. Shoulder


124




a


thus serves to maintain a drawer in the closed position until a user exerts sufficient force on a drawer to move embossment


112


past shoulder


124




a.






After embossment


112


has overcome raised shoulder


124




a


, the force of spring


82


tends to pull sliding plate


78


in first direction


64


. If cable


74


is in a low slack condition, however, sliding plate


78


will not be able to move in first direction


64


because engagement lug


104


will be prevented from moving in first direction


64


by the low slack cable. If the cable has little slack, further rotation of cam


80


in direction


126


will only be able to continue until a stop surface


128


on cam


80


abuts against embossment


112


. This condition is illustrated in FIG.


7


. Once stop surface


128


comes into contact with embossment


112


, further rotation of cam


80


in direction


126


is impossible. The degree of rotation of cam


80


when embossment


112


is in engagement with stop surface


128


is insufficient to allow engagement member


86


to exit from channel


120


. If a person attempts to open the associated drawer, the force they exert in the first direction will be transferred from engagement member


86


to cam


80


. Cam


80


will transfer this force to embossment


112


via its contact with stop surface


128


. Due to the construction of cam


80


, the force exerted by stop surface


128


against embossment


112


will generally be a vertical force that is perpendicular to first direction


64


. The force exerted on sliding plate


78


through embossment


112


will therefore not tend to move sliding plate


78


in either first direction


64


or second direction


66


. The pressure of stop surface


128


against embossment


112


will therefore not create any forces on engagement lug


104


. Cable


74


is therefore shielded from the forces exerted on the drawer when the cable is in a low slack condition. Surface


121


of channel


120


prevents cable


74


from pulling plate


78


in direction


66


as another drawer is attempted to be opened.




If cable


74


is not in a low slack condition when cam


80


rotates in direction


126


, then sliding plate


78


will be free to move in first direction


64


after embossment


112


has cleared raised shoulder


124




a


. This movement of sliding plate


78


in first direction


64


will cause embossment


112


to also move in first direction


64


. This movement of embossment


112


will allow it to fit into a channel


130


defined on cam


80


. Channel


130


is suitably dimensioned to allow cam


80


to continue to rotate until channel


120


is angled enough to allow engagement member


86


to exit channel


120


. Thus, the drawer can be opened. The movement of embossment


112


into channel


130


, which is caused by the biasing force of spring


82


, will also cause engagement lug


104


to move in first direction


64


. The movement of engagement lug


104


in first direction


64


will remove the slack in cable


74


and change the cable to a low slack condition. No other drawers will therefore be able to be opened simultaneously.




When the associated drawer is closed, engagement member will cause cam


80


to rotate in a direction opposite to the direction of its rotation when the drawer is opened. This closing rotation will cause a surface


131


on cam


80


to engage embossment


112


. This engagement pushes embossment


112


, and consequently sliding plate


74


in second direction


66


. In order to avoid requiring excessive force to close the drawer, surface


131


may be angled at about


45


degrees when it contacts embossment


112


. This allows sliding plate


78


to be pushed in second direction


66


without excessive forces.




Engagement member


86


, which is depicted in more detail in

FIG. 17

, is attached to an elongated member


132


. Elongated member


132


is fixedly secured to the drawer. Elongated member


132


is positioned on top of the drawer slide


70


. Elongated member


132


includes various apertures that may be used to secure it to the drawer


62


. Elongated member


132


includes a lower flange


134


that may be used to mount member


132


to drawer slide


70


(FIG.


18


). Rivet


88


and spring


82


are depicted in

FIGS. 19 and 20

, respectively.




Cable guide


84


, which is depicted in more detail in

FIGS. 21-23

serves to ensure that cable


74


is properly maintained in contact with engagement lug


104


of sliding plate


78


. Cable guide


74


may be manufactured of molded plastic. Cable guide


84


preferably snap-fittingly receives cable


84


so that cable


74


may be easily threaded into guide


84


with little danger of cable


74


becoming unthreaded. Cable guide


84


includes an upper and lower portion


136




a


and


b


. Channel


106


is defined between upper and lower portions


136




a


and


b


. As has been described, channel


106


provides clearance for sliding plate


78


and engagement lug


104


. Cable guide


84


includes two glide surfaces


138


that provide support to sliding plate


78


. Each portion


136




a


and


b


further includes an aperture


140


. Apertures


140


receive bent flanges


98


of attachment plate


76


when cable guide


84


is attached thereto.




Apertures


140


are spaced apart in a vertical direction a distance that is slightly smaller than the vertical distance between shoulders


100


on flanges


98


of attachment plate


76


. Thus, when flanges


98


are inserted into apertures


140


, shoulders


100


contact and press against inner surfaces


142


of apertures


140


. The dimensions of shoulders


100


force inner surfaces


142


to flex inwardly towards each other. When flanges


98


have been completely inserted into apertures


140


, shoulders


100


have moved past inner surfaces


142


, allowing them to flexibly snap back to their unstressed position. Shoulders


100


contact surfaces


144


of cable guide


84


. Shoulders


100


thus prevent flanges


98


from being retracted out of apertures


140


without flexing inner surfaces


142


towards each other. Because shoulders


100


do not have a cam surface that facilitates removal of flanges


98


from apertures


140


, cable guide


84


is securely retained on flanges


98


of attachment plate


76


. After cable guide


84


is secured to flanges


98


, sliding plate


78


is inserted into channel


106


between top and bottom portions


136




a


and


b


of cable guide


84


. When sliding plate


78


is so positioned in channel


106


, top and bottom portions


136




a


and


b


are substantially prevented from flexing toward each other by sliding plate


78


's contact with glide surfaces


138


. Cable guide


84


is therefore securely retained on attachment plate


76


.




Cable


74


is easily threaded into cable guide


84


by moving cable


74


in direction


146


into channel


106


(FIG.


21


). Movement of cable


74


in this direction causes the cable


74


to come in contact with two flexible arms


148


. As cable


74


is further pushed against flexible arms


148


, flexible arms


148


begin to flex out of the way until sufficient clearance is provided for cable


74


to pass by flexible arms


148


. As soon as cable


74


passes by arms


148


, they snap back to their unflexed condition. In this unflexed condition, cable


74


is prevented from being retracted out of cable guide


84


in a direction opposite the direction


146


by flexible arms


148


. If an interlock


72


is to be removed from the inside of a cabinet, cable


74


can be easily removed from cable guide


84


by manually pressing flexible arms


148


in direction


146


. Flexible arms


148


are pressed until sufficient clearance is provided for cable


74


to be retracted out of guide


84


in a direction generally opposite to direction


146


.





FIGS. 4 and 5

illustrate a pair of interlocks


72




a


and


b


in different conditions. The cable


74


in

FIGS. 4 and 5

is in a low slack condition. The drawer that is attached to the drawer slide of interlock


72




b


is in a closed position. As has been described previously, first surface


122


of cam


80


is in contact with embossment


112


in this position. The drawer corresponding to interlock


72




a


illustrates the condition of interlock


72




a


when this drawer is trying to be opened and cable


74


is already in a low slack condition due to either a lock or another interlock having its drawer open (not shown). Because cable


74


is in a low slack condition, engagement lug


104


of sliding plate


78


(of interlock


72




a


) is prevented from moving further in first direction


64


than that illustrated in

FIGS. 4 and 5

. Because sliding plate


78


cannot move further in first direction


64


, embossment


112


of sliding plate


78


cannot move out of the way of stop surface


128


on cam


80


. Embossment


112


thus prevents cam


80


from further rotation while cable


74


is in the low slack condition. Because cam


80


cannot rotate any further, engagement member


86


cannot disengage from channel


120


of cam


80


. The drawer therefore cannot be opened. As noted, cable


74


of

FIGS. 4 and 5

is in the low slack condition due to another interlock with an opened drawer (not shown) that is in communication with cable


74


. Alternatively, cable


74


could be in the low slack condition because it is in communication with a lock that has moved to the locking position.

FIG. 7

also illustrates an interlock


72


for a drawer that is trying to be opened when cable


74


is in the low slack condition. Again, the low slack condition of cable


74


is due to either a lock or another interlock that is not shown in FIG.


7


.




FIGS.


3


and


24


-


27


illustrate interlock


72


in its various positions according to different drawer conditions.

FIG. 3

illustrates interlock


72


when the associated drawer is closed.

FIG. 24

illustrates interlock


72


when the cable


74


has been changed to the low slack condition by an unillustrated interlock or lock and the drawer associated with interlock


72


is trying to be pulled open. The drawer is prevented from being opened by the engagement of stop surface


128


with embossment


112


. Because stop surface


128


presses vertically down on embossment


112


, sliding plate


78


does not experience a linear force in either first or second direction


64


or


66


. Whatever force is exerted against the drawer in first direction


64


is therefore not translated to cable


74


. Rather, cable


74


only experiences a tensioning force from interlock


72


that is due to spring


82


acting to pull engagement lug


104


in first direction


64


. The tensile strength of cable


74


therefore does not appreciably limit the amount of force that can be applied to trying to open the locked door before the interlock system fails. Interlock


72


of the present invention may resist up to


150


pounds of force on a drawer, or more, before it fails. Further, this failure point will be due to cam


80


and its interaction with either embossment


112


or engagement member


86


, not the tensile strength of cable


74


. Interlock


72


thus shields cable


74


from the forces that are applied in first direction


64


to open locked drawers.





FIG. 25

depicts interlock


72


in the position it would move to when a person was trying to simultaneously open two drawers in the cabinet. Because no single drawer is fully open, cable


74


includes sufficient slack to allow embossment


112


to almost move past stop surface


128


. However, embossment


112


cannot totally clear stop surface


128


, and neither drawer will be able to be opened in this situation due to the partial engagement of stop surface


128


with embossment


112


.





FIG. 26

illustrates an interlock


72


in which the drawer associated with interlock


72


is partially open. As can be seen, embossment


112


has moved into channel


130


of cam


80


. This has allowed cam


80


to rotate sufficiently to allow engagement member


86


to disengage from cam


80


. The complete disengagement of engagement member


86


from cam


80


is illustrated in FIG.


27


.

FIG. 27

illustrates the condition of interlock


72


when the drawer is open to a greater extent than that depicted in FIG.


26


. When the drawer of interlock


72


is moved back to its closed position, cam


80


must be oriented so that engagement member


86


can slide back into channel


120


. In order to prevent cam


80


from inadvertently rotating out of this orientation while the drawer is fully opened, cam


80


can be appropriately weighted so that it is unlikely to rotate when engagement member


86


is disengaged. This weighting can be adjusted by cutting holes in cam


80


at appropriate locations to remove weight, such as hole


127


(FIGS.


14


-


16


). Another flange, such as flange


129


(

FIGS. 14-16

) may also be added to increase the weight of cam


80


on a selected side of its pivot axis. Flange


129


may also be used to provide additional structural strength to cam


80


to help resist excessive pulling forces from engagement number


86


when the drawer is locked, but being attempted to be opened.




An example of a lock


216


that may be used in conjunction with the present invention is depicted in

FIGS. 30-32

. Lock


216


selectively changes the condition of cable


74


from a high slack condition to a low slack condition. Lock


216


includes a hole


260


, which may be a keyhole, into which a key may be inserted, or which may receive a bar that is coupled to a conventional lock cylinder. If hole


260


is a keyhole, insertion of the proper key therein allows a key cylinder


218


to be rotated by the key. If hole


260


receives a bar, which may be desirable where lock


216


is positioned at the back end of the cabinet, the bar is coupled to any conventional lock in a manner that causes the bar to be able to rotate about its longitudinal axis when the proper key is inserted into the conventional lock. In either situation, key cylinder


218


therefore will rotate when a proper key is used. Key cylinder


218


includes a pin


220


that moves in a cam track


222


defined in a reciprocating member


224


. Reciprocating member


224


is snap-fittingly attached to a cover


226


by way of a flexible arm


228


. Flexible arm


228


fits into an aperture


230


defined in cover


226


. Flexible arm


228


includes a shoulder


232


that retains reciprocating member


224


to cover


226


when the two are snap fit together. The snap fitting occurs when flexible arm


228


initially contacts cover


226


. A cam surface


234


causes flexible arm


228


to flex as reciprocating member


224


is initially pushed toward cover


226


. After the two are completely secured together, flexible arm


228


snaps back to its unflexed condition in which shoulder


232


prevents the two members from being separated.




Reciprocating member


224


includes a pair of apertures


236


. Cable


74


may be secured to one of the apertures


236


. When key cylinder


218


is rotated toward a locking condition, reciprocating member


224


moves vertically upward with respect to cover


226


(FIGS.


30


-


31


). This vertical movement decreases the slack in cable


74


such that no drawers in the cabinet may be opened. When lock


216


is unlocked, the unlocking rotation of key cylinder


218


moves reciprocating member


224


vertically downward with respect to cover


226


(FIG.


32


). This creates sufficient slack in cable


74


for a single drawer to be opened. Cover


226


may be securely fastened inside of cabinet


60


in any suitable manner.




Cable


74


may be secured to one of apertures


236


by threading the cable therethrough and tying it, such as is illustrated in

FIGS. 28-31

. Alternatively, a more preferred method of securing cable


74


to apertures


236


is accomplished by way of a J-hook


300


(FIG.


32


). J-hook


300


is crimped onto an end of cable


74


in a conventional manner. J-hook


300


includes a lower vertical section


302


, a middle horizontal section


304


, and an upper vertical section


306


. Upper vertical section


306


, along with a portion of horizontal section


304


, is inserted through one of apertures


236


and manipulated until upper vertical section


306


contacts one side of the wall in which apertures


236


are defined and is oriented vertically. In this position, horizontal section


304


passes horizontally through the aperture


236


and lower vertical section


302


abuts against a side of the wall in which aperture


236


is defined that is opposite the side contacting upper section


306


. In this position, J-hook


300


is maintained in aperture


236


and can only be released by manually twisting J-hook


300


appropriately to allow upper section


306


to be backed out of aperture


236


. J-hook


300


thus provides a convenient way for installing and removing cable


74


from lock


216


.




The opposite end of cable


74


may also be fastened within a cabinet by using a J-hook that fits through an aperture attached to the cabinet, although any other method of securing cable


74


can be used with the present invention. If it is desired to avoid having an end of cable


74


be attached to the frame of the cabinet, it could alternatively be held in place by interacting with cable guide


84


. Specifically, an enlarged ring or other structure could be affixed to the end of the cable. This enlarged structure would be dimensioned so that it was too large to pass through the cable passageway defined in cable guide


84


. For securing the bottom of the cable, the enlarged structure would thus abut against a bottom surface


310


of the lower-most cable guide


84


(FIGS.


21


-


23


). If it were desired to secure the top end of the cable in a like manner to a cable guide


84


, rather than to a lock


216


, an enlarged structure could also be attached to the top end of cable


74


. In this situation, the enlarged structure would abut against a top surface


312


of the uppermost cable guide


84


. The enlarged structure may preferably be shaped to snap onto, or otherwise be secured to, cable guide


84


. If an enlarged structure were used on both ends of the cable to secure it in the cabinet, the proper cable slack could be set by manufacturing the cable to the specific length that created the desired amount of slack.




Lock


216


could be modified so that reciprocating member


224


utilized a spring or other structure that selectively increased or decreased the tension on cable


74


. In other words, rather than having reciprocating member


224


absolutely move to is raised position when the key is rotated to the locked position, lock


216


could be modified to include a spring, or other biasing force, that urged member


224


towards its upper, locked position. If no drawers were open, this biasing force would be sufficient to raise member


224


to its locked position. If one drawer were open, this biasing force would be insufficient to move the member


224


to its upper position because the cable would be in its low slack condition, thereby preventing member


224


from moving upward while the drawer was opened. As soon as a drawer was closed, however, the biasing force would move member


224


to is locked position and remove the slack in the cable that was created by the drawer closing. This arrangement allows the lock to be switched to the locked position while a drawer is still open. Once the drawer closed, it would immediately be locked and not able to be opened until the lock


216


was deactivated. The modified lock


216


thus would allow the cabinet to be locked while a drawer was still open, and as soon as the open drawer was closed, it would immediately lock. Thereafter, no drawers could be opened until the lock was deactivated. The biasing force exerted on reciprocating member


224


in modified lock


216


should be sufficient to remove the slack in cable


74


when all the drawers are closed and to maintain the cable in the locked, low slack condition when pulling forces are exerted against one or more locked drawers.




Lock


216


may be further modified to include a solenoid, or other electrically controlled switch, that controls the movement of reciprocating member


224


between its locked and unlocked position. The solenoid could be controlled remotely by a user using a hand-held device that transmitted wireless signals to a receiver in the cabinet that controlled the solenoid. The control could be carried out in a conventional manner, such as in the manner in which remote, keyless entry systems work on many current automobiles. Alternately, the cabinet could include a keypad, or other input device, in which the locking or unlocking of the cabinet was controlled by information, such as a code or password, input by a user.




While other materials may be used, interlock


72


may be made primarily of metal. Specifically, attachment plate


76


, sliding plate


78


, cam


80


, and rivet


88


may all be made of metal, such as steel, or any other suitable metal. Engagement member


86


may be made of metal or any other suitable material. Cable guide


84


may be made from molded plastic, or any other suitable material. Drawer slide


70


is preferably made of metal, such as steel, with the exception of the ball bearing cages


166


for the ball bearings, which may be made of plastic. Spring


82


of interlock


72


may exert a force of approximately 1.5 pounds. Other spring strengths may, of course, be used. Cable


74


may be a steel cable composed of seven strands, with each strand made of seven individual filaments. Cable


74


may have a tensile strength of 40 pounds. Cable


74


may preferably be made of stainless steel and include a vinyl coating. The diameter of cable


74


after coating may be 0.024 inches, although other dimensions can be used. To avoid kinking of cable


74


, surfaces that come in contact with cable


74


, such as engagement lug


104


, may be curved with a radius of at least 0.125 inches to help reduce the possibility of kinking. As several possible alternatives to steel, cable


74


could be a string, a plastic based line, such as those used as fishing lines, or any other elongated, flexible member with suitable tensile strength.




A single interlock


72


is all that is needed for each drawer in the cabinet. The opposite drawer slide can thus be a regular drawer slide with no interlock attached. Interlock


72


, of course, can be attached directly to the cabinet, rather than integrated with the drawer slide. During the installation of the interlock system into a cabinet, the slack in the cable may be easily set by securing one end of the cable, opening a single drawer, and then pulling the cable until substantially all of its slack is removed. The cable is then secured in that condition. When the drawer is thereafter closed, the cable will have sufficient slack to allow only a single drawer to be opened at a time. Alternatively, cables


74


could be manufactured at a preset length to fit different cabinet heights. The installer of the interlocks therefore could simply fasten the cable in the desired location and the length of the cable will create the appropriate slack to allow a single drawer to be opened. Once the appropriate length of a cable is determined for a given cabinet height, cables could be easily mass-produced by a manufacturer by simply cutting them to the appropriate lengths.




While the present invention has been described in terms of the preferred embodiments depicted in the drawings and discussed in the above specification, it will be understood by one skilled in the art that the present invention is not limited to these particular preferred embodiments, but includes any and all such modifications that are within the spirit and scope of the present invention as defined in the following claims.



Claims
  • 1. An interlock for a drawer positionable within a cabinet, said drawer being movable in the cabinet in a first direction toward an open position and in a second, opposite direction toward a closed position, said interlock comprising:an elongated, flexible member; a slack take-up mechanism engageable with said elongated, flexible member and movable between a higher slack position and a lower slack position, said higher slack position allowing said elongated, flexible member to exist in a higher slack condition, said lower slack position causing said elongated, flexible member to exist in a lower slack condition; a cam operatively coupled to said slack take-up mechanism and to said drawer, said cam adapted to switch the slack take-up mechanism from the higher slack position to the lower slack position when the drawer is moved in the first direction; and a biasing member adapted to exert a force against said take-up mechanism that urges said slack take-up mechanism toward said lower slack position.
  • 2. The interlock of claim 1 wherein said biasing member is a spring.
  • 3. The interlock of claim 2 wherein said force of said biasing member has a magnitude that is independent of the magnitude of a force exerted on the drawer in said first direction.
  • 4. The interlock of claim 3 wherein said slack take-up mechanism includes a slide movable in a linear direction generally parallel to said first direction, said slide including an engagement surface positioned to engage said cable.
  • 5. The interlock of claim 2 further including a stop that prevents said cam from switching said slack take-up mechanism from the higher slack position to the lower slack position when the elongated, flexible member is in said lower slack condition.
  • 6. The interlock of claim 5 wherein said cam is adapted to prevent said drawer from being moved to said open position when said cam engages said stop.
  • 7. The interlock of claim 4 wherein said stop is an embossment.
  • 8. The interlock of claim 1 wherein said elongated, flexible member is a cable.
  • 9. The interlock of claim 8 further including a cable guide attached adapted to snap-fittingly receive the cable from at least one direction.
  • 10. The interlock of claim 9 wherein said cable is in communication with at least one other drawer interlock associated with another drawer, said at least one other drawer interlock adapted to change said cable to said lower slack condition when the another drawer is moved to an open position.
  • 11. The interlock of claim 8 wherein said cable is in communication with a lock, said lock adapted to selectively change said cable between said lower and higher slack conditions.
  • 12. The interlock of claim 11 wherein said cable is in communication with at least one other drawer interlock associated with another drawer, said at least one other drawer interlock adapted to change said cable to said lower slack condition when the another drawer is moved to an open position.
  • 13. The interlock of claim 8 further including a second cable in communication with a lock, said lock adapted to selectively change said second cable between lower and higher slack conditions, said drawer being prevented from being moved to the open position when said second cable is in said lower slack condition, said second cable being in operative engagement with said slack take-up mechanism.
  • 14. A cabinet having at least one drawer movable within the cabinet in a first direction toward an open position and in a second, opposite direction toward a closed position, said cabinet comprising:a frame adapted to support said drawer when positioned within the cabinet; an elongated, flexible member positioned within said cabinet, said elongated, flexible member changeable between a lower slack condition and a higher slack condition; an interlock positioned within said frame and in operative engagement with said elongated, flexible member, said interlock adapted to prevent said drawer from moving to said open position when said elongated, flexible member is in said lower slack condition and to allow said drawer to move to said open position when said elongated, flexible member is in said higher slack condition; and a slack take-up mechanism attached to said interlock and adapted to change said elongated, flexible member from said higher slack condition to said lower slack condition when the drawer is moved from the closed position to the open position, said slack take-up mechanism adapted to exert a force on said elongated, flexible member that has a magnitude which is independent of a force applied in said first direction to the drawer when said drawer is substantially closed.
  • 15. The cabinet of claim 14 wherein said elongated, flexible member is a cable.
  • 16. The cabinet of claim 15 wherein said cable is in communication with at least one other drawer interlock associated with another drawer, said at least one other drawer interlock adapted to change said cable to said lower slack condition when the another drawer is moved to the open position.
  • 17. The cabinet of claim 15 wherein said slack take-up mechanism includes a slide movable in a linear direction generally parallel to said first direction, said slide including an engagement surface positioned to engage said cable.
  • 18. The cabinet of claim 15 wherein said slack take-up mechanism includes a biasing member adapted to exert a force against said cable that urges said cable toward said lower slack position whenever the drawer associated with said interlock is moved to the open position.
  • 19. The cabinet of claim 18 wherein said biasing member is a spring.
  • 20. The cabinet of claim 14 wherein said elongated, flexible member is in communication with a lock, said lock adapted to selectively change said elongated, flexible member between said lower and higher slack conditions.
  • 21. The cabinet of claim 14 further including at least one drawer slide attached to said drawer, said drawer slide movable between an extended position corresponding to the attached drawer's open position and a retracted position corresponding to the attached drawer's closed position, said interlock mounted on said drawer slide and adapted to prevent said drawer slide from moving to said extended position when said elongated, flexible member is in said lower slack condition and to allow said drawer slide to move to said extended position when said elongated, flexible member is in said higher slack condition.
Parent Case Info

This application claims priority to commonly-assigned U.S. Provisional Patent Application Serial No. 60/429,772, filed Nov. 27, 2002, the disclosure of which is hereby incorporated herein in its entirety by reference.

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Entry
U.S. patent application US 2002/0093274 A1 issued to Jackson, Jul. 18, 2002.
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Provisional Applications (1)
Number Date Country
60/429772 Nov 2002 US