Abstract:
A latch is disclosed incorporating features allowing complete actuation i.e., engagement and disengagement of a latching hook on the side of the container from a latch handle on the face of the container thus allowing actuation of the latch hook even when the latch hook is itself inaccessible. The latch also features variability in the stroke of the hook and a design allowing its construction from plastic material.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to latches. More particularly, the invention relates to latches which are engageable and disenageable from an easily accessible area to an otherwise inaccessible area such as when a latch is actuatable from a front of a container and the latch hook is on the side of the container, the side of the container being obscured by other containers. 
     2. Prior Art 
     In the ensuing discussion the types of latches described are generally referred to as front opening latches since the first surface perceived by a user is considered to be the “front” of the container. In the discussion of the prior art hereunder and in the discussion of the invention, the term “front” is used generically to indicate the exposed surface of the container. This could actually be, however, any surface of the container. 
     Front opening latches of the prior art have been developed for the same purpose as the present invention; that is to allow operation of the latch where containers are stacked next to one another obstructing access to the sides of the container. Since other conventional latches reside on the side of the container or require movement out of the plane of the side of the container, operation of these would be severely impeded. 
     Two main categories of prior art latches are intended to satisfy the desire/requirement for front operation latches. These are 1) side mounted latches that are operable when access to box sides is limited and 2) top mounted latches. 
     In the first category (side mounted), an example of an arguably “front only” actuatable latch is known by the trade name “Hook Lock” and is illustrated in FIG. 1 of this application. One of skill in the art will recognize this latch. The latch incorporates a cam design so that movement of the handle lever causes both an arcuate and a radial movement of the hook. Thus, upon moving the handle lever in the appropriate direction the hook moves into engagement with the keeper plate. Further movement of the lever in the same direction causes the hook to draw the keeper plate toward the cam of the handle lever. This action draws the container cover toward its base and provides a tight closure. The latch is sold as actuatable from the front only because if mounted in a recess in the container side, it is considered possible to slide one&#39;s finger between adjacent containers and actuate the latch without actually seeing more than the end of the lever. Clearly, this suffers the substantial drawback that the latch could not be actuated in this manner if the cover of the container was deep. If it were, the fingers of the user would not reach the latch. Thus, this type of latch is not a viable solution to the front only operation dilemma. 
     Top mounted latches provide more diversity in the front only operation forum since they truly operate from the exposed surface of the container. Prior art top mounted latches have certain inherent drawbacks with some types of containers (e.g., fluid tight containers). These latches thus leave the art searching for a better solution to the need for front only operation. 
     One type of top mounting latch is a bail spring latch such as that illustrated in FIG. 2 of the disclosure. This type of latch, although effective in closing and tensioning a container lid, requires a “through the container” mounting. In containers commonly employed for transport of sensitive equipment where a fluid tight seal is required at all times, these latches require a very effective (expensive) dynamic seal. Dynamic seals of this nature are cost prohibitive, subject to failure and therefore do not provide a preferred solution. 
     Other prior art latches whether top or side mounted which operate well for their intended purpose cannot work where adjacent structures are concerned because of their requirement that they move out of the side plane of the container or where they don&#39;t, they simply cannot be easily actuated from the exposed surface of the container. The adjacent structure inhibits the movement and/or access to these latches and prevents operation thereof. 
     SUMMARY OF THE INVENTION 
     The above-discussed and other drawbacks and deficiencies of the prior art are overcome or alleviated by the front opening latch of the invention. 
     Although “front” is employed in this specification as the location of operability of the latch disclosed herein, it will be understood that any plane of the container on which the latch is employed could be the operation plane or surface. More specifically, the latch body could be mounted on the front, top, side, bottom or rear of the container depending upon how the container is being viewed. The more important concept of the invention is that the latch is completely operable from an exposed plane or surface of the container, while acting on an adjacent surface which may be obscured from access or view. This is particularly advantageous when said containers are stacked one atop another or next to one another, etc. The most ubiquitous example of such use is, of course, where many of such containers are stacked in such a way that they create a wall. In this situation, a box in the middle could be opened if the invention is employed but could not have been opened if many of the prior art latches were installed. Since this scenario is most common and the exposed plane of the container is generally considered the “front” by most people, the term “front” has been used herein as the generic descriptor. Limitation is not intended. The invention also has no dynamic seals and is operable using only one hand. 
     An important feature of the invention is variability in the available stroke for drawdown. By varying the distance between certain components of the invention the stroke is increased or decreased. This benefit is achieved while not affecting the motion of the hook perpendicular to the side of the container. In other words the attachment of the hook to the latch lever, discussed hereunder in detail, does not need to move laterally during drawdown regardless of the stroke of the latch. This concept cannot be achieved by the prior art and provides a significant advantage in function. 
     Another important feature of the invention is the designed in capability of the latch to be made from plastic materials. The latch is preferably made of thermoplastic polyester which would creep under loads normally associated with latches intended to secure covers to containers as is the current invention. To accommodate the loads in such a way that the desired material is employable, the surface area of load bearing components of the latch have been enlarged to enable sufficient strength of the inexpensive and relatively malleable material to be employed. 
     The latch of the invention generally comprises a latch body having several components mounted as a unit on one surface of a container and a hook that is disposed generally perpendicularly to the latch body and is selectively engageable with a strike mounted fixedly on a surface of the container adjacent the surface upon which the body is mounted. The latch operates over the generally perpendicular angle by facilitating control of the hook from a spring lever disposed on or in the body. 
     The latch develops about 100 lbf of closure force near the end of its stroke and securely holds the cover of the container in place and sealed. Operation force required by the user, however, remains very small at 10 lbf or less. 
     The latch is maintained in the closed position by either or both of an over-center pivot point arrangement relative to the principal drawdown force vector of the draw down assembly and a hold down catch in the latch body. 
     Another feature of the latch of the invention is a warning system indicating that the latch is not engaged. Since it is desirable to prevent the latch lever from being freely located beyond the outer plane of a container to which it is mounted (i.e., mounted in a recess), it is spring loaded to return to and stay in the down or closed position when it is disengaged. Since in this position the latch appears to be engaged it is advantageous in the preferred embodiment to provide a system to warn a user that the latch is not, in fact, engaged. This is provided by a movement within the body of the latch allowing a colored section to be visible if the latch is not engaged. This colored section is not visible when the latch is engaged. 
     The above-discussed and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring now to the drawings wherein like elements are numbered alike in the several FIGURES: 
     FIG. 1 is an illustration of a prior art latch having some ability to be actuated from the front of a container; 
     FIG. 2 is an illustration of a second prior art front operated latch where a dynamic seal is necessary for the function of the latch; 
     FIG. 3 is a perspective view of a section of a container on which the latch of the invention is mounted in the loaded and secured position; 
     FIG. 4 is a perspective view of a section of a container with the latch of the invention mounted thereon in the unlatched position; 
     FIG. 5 is an exploded perspective view of the latch of the invention; 
     FIG. 6 is a cross-section of FIG. 3 taken along Section Line  6 — 6 ; 
     FIG. 7 is a perspective view of the latch of the invention removed from the container and in a partially raised condition to illustrate pin movement within a groove; 
     FIG. 8 is the view of FIG. 7 with the closest wall of the base removed to provide a view of the interior of the latch of the invention; 
     FIG. 9 is an enlarged view of the groove in the latch of the invention; 
     FIG. 10 is a perspective view of the latch of the invention removed from the container wherein the lever of the latch is fully raised and the spring lever released; 
     FIG. 11 is a cross-section view of FIG. 10 taken along Section Line  11 — 11 ; 
     FIG. 12 is a bottom perspective view of the latch lever of the invention; 
     FIG. 13 is a perspective view of an alternate embodiment of the latch; 
     FIG. 14 is a bottom perspective view of the alternate latch lever; 
     FIG. 15 is a perspective view of the alternate base without other components; 
     FIG. 16 is a cross-section view of the latch taken along section line  16 — 16  in FIG. 13; and 
     FIG. 17 is a cross-section view of FIG. 7 taken along section line  17 — 17 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 3 and 6, the invention is illustrated in the engaged position. It will be appreciated from a review of these figures that the latch of the invention maintains all components on the exterior of the container to which it is attached, thereby requiring no dynamic seals. This is of great benefit to maintain the fluid tightness often required of the type of container for which the latch was developed. Additionally, this is a significant advance over prior art systems with respect to reliability and economy. 
     In order to understand the exteriorly visible componentry, reference to FIGS. 7,  8 ,  9  and  10  should be had. Latch body  10  comprises base  12  with bosses  14   a  and  14   b  for receiving screws from within container  16  to attach latch body  10  thereto. It should also be noted that upon boss  14   b  a catch  18  is located to receive a similar feature on the latch lever discussed hereunder. Catch  18  provides assurance that latch lever  30  stays in the closed position even under the forces (e.g., gravity, impact with other structures, etc.) sustained during the impact of a drop of for example of 10-20 inches by careless personnel or due to perhaps a stack of containers falling over. 
     Base  12  further includes trap support  19  and trap  22 . Trap support  19  is preferably a continuation of base  12  which extends over the edge of the plane upon which base  12  is supported. Trap support  19  functions to provide trap  22  which is desirable in a preferred embodiment to prevent the hook from moving more than necessary to clear the strike and to stay within the recess thereby not breaking the plane of the surface of the container. 
     In a preferred embodiment trap support  19  further includes an extension  20  perpendicularly oriented thereto. Extension  20  includes a tang  24  which is dimensioned to be received in a depression  26  (see FIG. 6) of the container  16  to provide further restraint for the trap  22 . In this preferred embodiment a container must be specifically manufactured to be fitted with this latch. The embodiment is preferred due to the superior strength thereof without the use of additional fasteners. It should be noted, however, that the latch of the invention can be constructed without extension  20  so as to be employable as a retrofit on containers which have not been specifically designed for use with front opening latches of the invention having extension  20 . 
     Referring to FIGS. 3-11 simultaneously, it can be seen that in operable communication with base  12  of latch body  20  is latch lever  30 . Preferably, latch lever  30  is nested within uprights  13  of base  12 . Lever  30  is required to articulate with base  12  to operate the mechanism of the invention. The articulation of lever  30  with base  12  is through an L-shaped groove  36  in base  12  and a dual pin system. The two pin structures  32  and  34  in communication with the base  12 , are designed to move in the L-shaped groove  36  to facilitate the desired movement of the various components of the invention (The terms pin structures are used here because there are actually two parts of each pin, the pin does not extend all the way across the latch. Hereafter the singular term pin will be employed for simplicity). It is important to note that pin  32  is a part of hook  38  (actually hook  38  splits at its upper extreme to form two hoops  38   a  and  b  to which the pins  32  are attached) and that movement of this pin causes the hook to move through its stroke. Since the desired movement of the hook  38  is substantially parallel to the principal force vector encountered in closing the container on which the latch is mounted, the section  36   a  of L-shaped groove  36  where hook pin  32  moves is also parallel to that principal force vector. Hook pin  32  is mounted in recess  31  of latch lever  30  so that lever  30  may rotate therearound and hook pin  32  transfers draw down force through the lever  30  to the cam surface  33  and then to base  12 . 
     Another important aspect of hook pin  32  is that it is mounted in such a way as to tend to keep the latch lever  30  closed. More specifically, hook pin  32  is mounted in recess  31  in lever  30  in a position allowing it to be just over-center of the cam surface  33  when the latch is in the closed position. This tends to maintain the latch in the closed position. 
     Referring specifically to FIGS. 8 and 9, latch pin  34 , as will be appreciated by a review of the drawings, has an unusual shape. The shape is important to operation of a preferred embodiment because it provides movement in desired directions only. Importantly, latch pin  34  having a generally triangular appearance facilitates features of the invention such as a latch open flag, positive return of the lever  30  to the closed position and urging of the hook downwardly for engagement or disengagement with the strike. From a review of FIGS. 8 and 9, one of ordinary skill in the art will note that angled surface  35  of latch pin  34 , which is preferably about 45° to an imaginary horizontal reference in the drawing, never moves off inside radius  37  of L-shape  36  when the latch lever  30  is in the closed position and the hook is not engaged. This is because if surface  35  were to move off radius  37  in the vertical portion  36   a  of L-shape  36  (i.e., when lever  30  is in the closed and unlatched position) it would not be possible for an operator to lift lever  30  without first pushing and holding the end of lever  30  down against the base  12  to move tip  41  from wall  43  of groove  36 . It will be appreciated that if tip  41  is against wall  43 , the lever cannot move because the two pins  32  and  34  on each side of lever  30  work against each other in groove  36  to hold the lever  30  in a nearly static state. Providing surface  35  does stay on radius  37 , however, when lever  30  is raised, pin  34  merely slides across radius  37  and into the horizontal portion  36   b  of groove  36 . The plastic coefficient of friction for a material of choice is preferably at less than about 0.3. The ability to use plastic for the invention is occasioned by the particular construction which spreads the load experienced by the latch over a relatively large surface area. 
     It should be noted that latch pin  34  is offset relative to hook pin  32  in order to provide a sufficient length of surface  35  to prevent that surface from moving off radius  37 . Thus when latch pin  34  is to rotate due to lifting of lever  30 , additional space must be provided. If the space of area  45  is not provided, tip  41  would contact the top and bottom walls of groove section  36   b  simultaneously and would prevent lever  30  from being fully raised. Enlarged area  45  is of a shape complimentary to tip  41  of latch pin  34  so that these parts may easily fit into the enlarged area. Because area  45  allows latch pin  34  to rotate 90° in groove  36 , lever  30  is rotatable to the fully raised position. Tip  41  bears on radius  47  of area  45  to provide downward leverage to hook pin  32  through lever  30 . The hook is therefore urged downwardly toward the end of its stroke when latch pin  34  is in area  45 . A benefit is achieved by the arrangement of the latch lever in the base of the invention in that very little actuation force (less than 10 lbf, loaded) relative to the drawdown force (approximately 100 lbf) is needed to open or close the latch when loaded. The use if the preferred plastic material permits the friction coefficient to be maintained below 0.5 with no lubricant. 
     The latch of the invention substantially avoids perpendicular movement relative to the principal force vector of closure. With respect to the terms “avoids perpendicular movement relative to the principal force vector,” it is assumed that firstly that one of ordinary skill in the art will appreciate that there is a principal force vector in a latch mechanism; secondly that the principal force vector existing in the latch of the invention will be along the hook since it is designed to be there and based upon the operation of components, that is where it in fact is; and thirdly that perpendicular movement relative to a vector, includes any movement having a perpendicular component to its movement. This is not to say that the pin  32  necessarily must move in the principal force vector but that it must move in a direction substantially parallel with that vector. The parallel movement may be within the vector but also may be outside the vector. 
     By moving lever  30  to the raised position the hook pin  32  is allowed (and urged against the bias of spring  58  by continued upward movement of lever  30 ) to move toward the strike  39  causing the loading force of hook  38  against strike  39  to be released. During re-engagement of the latch of the invention (assisted by the operation of spring lever  50  discussed hereunder), hook pin  32  is moved away from strike  39  with hook  38  catching strike  39 . The draw down force created hereby is transmitted to the container cover and compresses a seal (not shown) on the parting line securing the cover to the base of the container. The mechanism of movement of the pin  32  toward strike  39  in the present invention provides the additional benefit of variability in the stroke of the hook  38 . By altering the distance between cam surface  33  and hook pin  32  as well as the length of the both portions of L-shape groove  36 , the effective stroke of the hook can be varied. The larger the distance between pin  32  and cam surface  33  (and commensurate lengthening of the groove  36 ), the longer the stroke of the hook. This variability is available while maintaining the hook pin movement to a direction parallel to and proximate to the principal force vector during drawdown. This feature makes the latch of the invention extremely versatile while maintaining the other discussed benefits thereof. 
     In addition to the construction of the over-center pin position, referring to cross-section drawing FIGS. 6 and 11, lever  30  is maintained in the “down” position, redundantly, whether engaged or disengaged, by detent  40  which is preferably a downstruck projection from a center section of the latch lever  30  and positioned to align lip  42  of detent  40  with catch  18  of boss  14   b . When the latch lever  30  is fully in the down position, lip  42  is engaged with catch  18  and remains in that position until deflected into disengagement by, in a preferred embodiment, button  44  located on the surface of latch lever  30 . In a preferred embodiment, button  44  is provided by severing the surface material of latch lever  30  on three sides to create a cantilevered portion that is easily deflected by placing pressure on the end thereof. Deflection ease of button  44  is assisted by chamfer  61  on lever  30  to permit a user&#39;s finger more room to deflect button  44 . 
     Each of the components of the latch of the invention are assisted in operation by a single spring. Spring  58  is located and secured in base  12  and provides cantilever spring tongue  59  to interact with other components as discussed hereunder. Spring  58  includes feet  63  (see FIGS. 5 and 17) at the ends of legs  65  which are provided to secure the spring. Feet  63  are adapted to fit within blocks  67  while legs are placed under leg holders  69 . It will be appreciated that these features are well illustrated on one side of the latch in FIG. 8, however the features are identically provided on the other side of the latch in a preferred embodiment. By employing a single spring for all functions, complexity, cost and assembly time are reduced. To understand operation of spring  58 , spring lever  50  must first be introduced. Spring lever  50 , best illustrated in FIG. 5, is preferably nested in latch lever  30  and pivotally mounted therein on spring pivot pins  52 . The pivot action of lever  50  facilitates one finger deflection of cantilever spring tongue  59  by depressing trigger surface  56 . Movement of spring tongue  59  is caused by spring tongue cam  54  bearing thereupon occasioned by actuation of trigger  56  (and by raising latch lever  30 ). The movement imparted to spring tongue  59  by tongue cam  54 , causes it to bear against landing  60  on or in hook  38 . (It should be noted that landing  60  can be created by opening a hole in hook  38  (as illustrated) or by providing a projection from the rear surface thereof at an appropriate location to intersect with spring tongue  59 . Determining where to place the hole or projection is a matter easily accomplished by one of ordinary skill in the art following exposure to this disclosure and can be viewed representatively in the figures.) Returning to the operation of the invention, by urging spring tongue  59  toward container  16 , hook  38  is biased outwardly away from container  16  at roughly 90° to the direction of movement of spring tongue  59  and downwardly. This movement enables the movement of hook  38  with respect to strike  39  to disengage the latch of the invention. Actuating of trigger  56  is necessary to this movement since without actuating trigger  56  the natural bias of spring  58  is away from container  16 . The natural bias is useful during a disengagement operation since it provides the impetus needed to misalign hook  38  with strike  39  and facilitate the disengagement of the latch. 
     During the disengagement operation, when latch lever  30  is opened (moved away from container  16 ) without actuating the spring lever, the hook  38  is biased upwardly and outwardly by the spring. When the load on the strike is removed, the natural bias of spring  58  moves hook  38  into misalignment with strike  39  and the latch is disengaged. When the lever  30  is released, it is urged down into the closed position by the continued upward urging force of the spring on hook  38 . 
     Reengagement of the latch of the invention is a simple one hand operation. Lever  30  is raised to the upright position and trigger  56  is actuated. These two actions cause hook  38  to be urged into a position where it is aligned with strike  39 . Lever  30  is then moved back to the closed position while holding trigger  56  and hook and strike engage and provide draw down force to the cover of container  16 . Upon restoring latch lever  30  to the closed position, approximately 100 lbf of draw down force is developed in hook  38  and detent  40  snaps lip  42  into engagement with catch  18  of boss  14   b.    
     In a preferred embodiment of the invention the exact placement of pin  32 , size and shape of pin  34  as discussed and the length of groove  36  is important for a safety feature. Since the latch lever is always biased into the closed position it would be difficult to know if the container was indeed latched shut without checking each of the latches. Visually checking the hook and strike of the latches can be extremely difficult in a wall of containers for the same reasons front operation latches are needed. To alleviate this time consuming, difficult, and often inconclusive procedure, the inventor hereof has devised a warning system as follows and is illustrated in FIG.  4 : By allowing room at the top of groove  36 , pin  32  is permitted to move high enough to allow latch lever  30  to become slightly unnested in base  12 . Pin  34  also moves up groove  36  but as previously stated never moves beyond radius  47 . Lever  30  moves upwardly from base  12  approximately ⅛ th  inch by the natural bias of spring  58  when hook  38  is disengaged from strike  39 . By providing a brightly colored surface  70  on each side of latch lever  30  that is only visible when the latch lever has been elevated by the ⅛ th  inch due to the hook  38  not being engaged, a quick visual check of the latch will immediately inform the user as to the condition of the latch. When the latch is fully engaged the brightly colored surfaces are completely concealed by upright members  13  of base  12 . 
     An additional and significant benefit of the latch of the invention apart from its fully front only operability is that the forces developed and encountered by the operation of the latch are placed and oriented in such a way that a plastic material such as a thermoplastic polyester, preferably Valox™ can be employed to make these parts. In fact, all parts except the spring  58 , hook  38  and strike  39  in the preferred embodiment are constructed of plastic. Spring  58  is preferably constructed of stainless spring steel although other materials could be substituted, as is recognized by one of skill in the art, including plastic. Strike  39  and hook  38  are preferably constructed of aluminum (although again other materials could be substituted which have a yield strength of higher than 40,000 psi). 
     Referring to FIG. 12, lever  30  is illustrated apart from all other parts of the invention and from the bottom to illustrate structure that makes possible the employment of plastic material. As can be appreciated from FIG. 12, cam surface  33  is made up of preferably four force bearing surfaces  33   a-d . These surfaces distribute the static closure force of the latch. The surface area to be provided is selected so that with a static closure force of 30 lbs, the compressive stress is less than 500 psi and the long term strain at the maximum operating temperature will be less than 2%. The arrangement enables the latch lever cam surface  33  to withstand extended use without significant creep(causing failure or reduction of efficiency). Another area of concentration of forces on a plastic surface is at recess  31 . The recesses are each dimensioned to achieve a large surface area to spread the forces experienced. One of ordinary skill in the art having been exposed to this disclosure will recognize that pin  32  of hook  38  is significantly larger than it might be if the latch was constructed of metal. Also visible in FIG. 12 are finger rest protuberances  29  which act both to strengthen the latch lever  30  and to provide comfort to the user. 
     It will be understood that the latch of the invention can certainly be constructed of material other than plastic (e.g. metal) and may employ surface areas for bearing loads which are below those preferred herein for the use of plastic. This is due to the inherent structural rigidity of metal and should be appreciated by one of skill in this art. 
     In an alternate embodiment of the invention, several features are modified. Referring to FIGS. 13-16, button  144  is visible. Button  144  replaces button  44  in the previous embodiment. Button  144  includes downstruck member  140  with lip  142  to engage catch  118  on boss  114   b . Button  144  is articulated within latch lever  130  on pin  170  in boss  172  on either side of latch lever  130 . Button  144  and member  140  are together actuable by depressing button  144  downwardly against spring  174  to disengage lip  142  from catch  118 . Button  144  further includes stop  176  to maintain button  144  in the appropriate position when lip  142  is not engaged with catch  118 . In a preferred arrangement, button  144  includes ridges  178  for a sure grip. This embodiment is identical in all other respects with the previous embodiment except for the extension and tang of the prior embodiment. In the present embodiment there are two extensions  120  and two tangs  124  as illustrated in FIG.  13 . These function in the same way as the prior embodiment. 
     While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustration and not limitation.