Latch assembly

An improved latch assembly adapted particularly for use in the electronics or communications industry to retain a plug member in electrical engagement with a receptacle and prevent relative movement therebetween in a latching direction. The latch assembly includes a first latch member adapted for limited movement in a direction generally parallel to the latching direction between first and second positions and for limited movement in a direction generally perpendicular to the latching direction between engaged and disengaged positions. The latch assembly further includes a spring member for biasing the first latch member toward an engaged position, a stop member for limiting the movement of the first latch member in a direction opposite the latching direction and a guide member for causing movement of and guiding the first latch member toward its second position during movement of the latch member toward its disengaged position.

BACKGROUND OF THE INVENTION 
The present invention relates generally to an improved latch assembly, and 
more particularly, to an improved latch assembly for a monitor or patch 
cord plug or the like usable in the electronics or communications 
industry. 
The prior art includes a great many different types and forms of latches 
for securing or retaining one member or element in a relatively fixed 
position with respect to another. In particular, various types of latch 
mechanisms and assemblies exist in the electronics and communications 
industry. These latch mechanisms may, among other things, be used to 
secure or retain a plug member in fixed relationship with a receptacle to 
insure electrical connection between the plug and receptacle and to avoid 
accidental or inadvertant disengagement of the members. A specific example 
of a latching assembly or mechanism in the communications industry 
involves the incorporation of such an assembly or mechanism in a monitor 
or patch cord plug to retain the same in a circuit monitoring module. More 
particularly, such latch mechanism includes a unitary piece of spring 
metal securely seated and retained within the plug member. This spring 
member includes a shoulder portion which, upon insertion of the plug into 
the receptacle or module, engages a corresponding shoulder portion, and a 
curved portion joining the shoulder portion with the portion secured to 
the plug and imparting an engaging force to the shoulder. The shoulder of 
the spring member is designed so that it can be manually depressed when 
removal of the plug is desired. When not depressed, this shoulder portion 
serves to retain the plug member within the receptacle to ensure 
electrical contact therebetween. 
One problem which exists in the art with respect to most latch members 
arises when someone attempts to disengage the members that are latched 
together without first properly releasing the latch mechanism. This is 
particularly true with respect to latches in the electronics and 
communications industry since users often attempt to disengage the plug 
member from the receptacle by pulling on the cord connected to the plug or 
by pulling on the plug member itself without depressing or otherwise 
releasing the latch assembly. As a result, significant stress is placed on 
the latch assembly, and particularly the latch spring, to the point where 
it "cams-out" or prematurely releases, eventually resulting in its 
inability to properly serve as a latching mechanism. 
Accordingly, there is a real need in the latch assembly field and 
particularly, in the latch assembly field as applied to the electronics 
and communications industry for a latch assembly capable of withstanding 
the forces caused by attempts to remove the plug without properly 
releasing the latch mechanism and ensuring that even if the latch releases 
under these conditions, the mechanism does not lose its latching ability. 
SUMMARY OF THE INVENTION 
The present invention relates generally to an improved latch assembly, and 
more particularly, to an improved latch assembly usable in retaining a 
plug member in association with a receptacle. In contrast to the prior 
art, this improved latch prevents premature disengagement of the members 
under normal forces, unless the latch is first released, and ensures that 
the latch assembly will retain its ability to serve its latching function 
despite repeated attempts to remove the plug without properly releasing 
the latch mechanism. More specifically, the latch assembly of the present 
invention functions to prevent movement in a latching direction of a first 
element or plug relative to a second element or receptacle and includes a 
latch member associated with the plug element. The latch member is adapted 
for limited movement generally parallel to the latching direction of the 
assembly between first and second positions and for limited movement to a 
direction generally perpendicular to the latching direction between an 
engaged position and a disengaged position. This latch member includes a 
shoulder portion for latching engagement with a corresponding shoulder 
portion of the receptacle. A latch spring or bias means is associated with 
the latch member to impart the necessary latching force thereto. The latch 
assembly of the present invention also includes a stop member for limiting 
movement of the latch member in a direction opposite the latching force. 
This stop member functions to relieve forces on the latch spring resulting 
from attempted disengagement without properly releasing the latch. This 
significantly prolongs the life of the latch assembly and increases the 
force necessary to disengage the assembly when the latch is not properly 
released. The latch assembly of the present invention also includes a 
guide means for causing movement of and guiding the latch member in the 
latching direction during movement of the latch member toward its 
disengaged position. This guide means functions to further increase the 
force necessary to disengage the plug and receptacle elements, without 
first releasing the latch. 
Accordingly, it is an object of the present invention to provide an 
improved latch assembly for preventing movement in a latching direction of 
a first element relative to a second. 
Another object of the present invention is to provide an improved latch 
assembly usable in the electronics and communications industry to retain a 
plug member in association with a receptacle. 
Another object of the present invention is to provide an improved latch 
assembly capable of avoiding accidental or inadvertent disengagement of 
the latched members without properly releasing the same. 
A further object of the present invention is to provide an improved means 
for relieving the forces exerted on the latch spring when the latched 
elements are attempted to be disengaged without properly releasing the 
latch assembly. 
Another object of the present invention is to provide a latch assembly 
having an increased locking force. 
These and other objects of the present invention will become apparent with 
reference to the drawings, the description of the preferred embodiment and 
the appended claims.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Although it is contemplated that the latch assembly of the present 
invention can have many different applications, the preferred embodiment 
shows its use in the electronics or communications industry to retain a 
plug within a receptacle and to prevent accidental or inadvertent 
disengagement without first properly releasing the latch. The general 
operation of the latch assembly can be understood best by reference to 
FIG. 5. As illustrated, a first element or plug member 11, which in the 
preferred embodiment is a monitor or patch cord plug, is adapted for 
insertion into a corresponding second element or receptacle 40. When fully 
inserted, electrical engagement occurs between corresponding contact 
elements in the respective elements 12 and 40. The plug 11 is retained 
within the receptacle 40 by the latch assembly which is comprised 
generally of the latch member 24 and the latch spring 19. The latch member 
24 includes a shoulder portion adapted for corresponding engagement with a 
shoulder portion of the receptacle to provide latching engagement between 
the plug 11 and receptacle 40 in a latching direction. As shown in FIG. 5, 
the latching direction of the preferred structure is indicated by the 
directional arrow 13. When disengagement of the latch assembly and removal 
of the plug is desired, the latch member 24 is manually depressed at the 
point 41 and the plug 24 withdrawn. 
The structural details of the present invention can be best understood by 
first referring to FIG. 1 showing a pictorial, exploded view of the plug 
and latch assembly. As illustrated, the monitor plug 11 includes a 
generally rectangular portion 12 housing the circuitry and various other 
operative elements of the plug and a forward section 14 extending from one 
end of the rectangular portion 12. This forward section 14 is intended for 
insertion into the receptacle and generally includes the contact elements 
for electrically engaging corresponding contact elements in the 
receptacle. The forward portion 14 further includes a guide rib 15 for 
ensuring proper orientation of the plug 11 in the receptacle. The plug 11 
also includes an elongated latch assembly seat 16 into which the latch 
assembly 10 is disposed. The seat 16 is elongated in the general direction 
of the longitudinal axis of the plug member 11 and the latching direction 
and extends over portions of the rectangular and forward portions 12 and 
14 of the plug. 
The latch assembly 10 includes a bias means or latch spring member 19 
having a forward end 20, a rearward curved portion 21 and an intermediate 
portion 22. The function of the bias or spring member is to bias or urge 
the latch member 24 toward its engaged position. The latch member 24 is 
connected with an end of the spring member adjacent the curved portion 21 
and is movable relative to the spring 19 in a direction generally parallel 
to the longitudinal dimension of the spring 19 and generally parallel to 
the latching direction of the latch assembly. As shown, the latch spring 
19 is configured for positioning within the seat portion 16 of the monitor 
plug 11. 
As illustrated more specifically in FIG. 2, the bias or spring member of 
the preferred embodiment is an elongated leaf spring member. The forward 
end 20 of such spring member comprises an elongated, relatively flat piece 
of spring metal having a pair of holes 25 therein for engagement with a 
corresponding pair of posts integrally formed with the plug 11. The 
rearward portion of the forward end 20 is integrally joined with the 
elongated intermediate portion 22 of the latch spring and lies within the 
seat portion 16 (FIG. 1). The intermediate section 22 extends rearwardly 
to where it is joined with the curved portion 21. The curved portion 21 is 
curved about a radius through approximately 180.degree. to a point where 
it curves back toward the forward end of the latch spring 19. The curved 
portion is integrally connected through a stepped portion with an end 
section 26 which extends into and slidably supports the latch member 24. 
As illustrated best in the sectional view of FIG. 3, the elongated end 
portion 26 of the latch spring extends into a corresponding elongated slot 
or opening 28 in the latch member 24 for guiding and supporting the same. 
The slot or opening 28 is slightly larger than the exterior dimensions of 
the portion 26 to permit relative sliding movement between the latch 
member 24 and the latch spring portion 26 in a direction generally 
parallel with the longitudinal axis of the spring 19 and generally 
parallel to the latching direction 13 (FIG. 5). The sliding movement of 
the latch member 24 occurs between a first or forward position and a 
second or rearward position. The end section 26 includes a shoulder 
portion 17 rearwardly spaced from the end of the portion 26 and adapted 
for engagement with an interior shoulder of the member 24 to limit the 
rearward sliding movement of the latch member 24 along the section 26 and 
to define the second or rearward position of the latch member. 
The spring member 19 also includes a finger or tab portion 23 integrally 
formed with the forward end of the spring and extending outwardly 
therefrom over a portion of the latch member 24. As will be discussed more 
fully below, the tab or finger 23 prevents the latch member 24 from 
sliding off the end portion 26 of the latch spring and allows for the bias 
means or curved portion of the spring 21 to be preloaded. A second tab 
member 27 extends from the lower surface of the elongated intermediate 
section 22 for securing the latch spring into engagement with the seat 16. 
It is contemplated that the latch spring 19 can be constructed of various 
types of spring metal, plastic or other materials which are sufficient to 
impart the necessary latching force to the latch member 24. In the 
preferred embodiment, the spring member 19 is constructed of a copper 
alloy which exhibits the necessary spring characteristics and which has 
been found to have excellent resistence to corrosion without the need for 
any protective coating such as plated nickel or cadmium. 
The details of the latch member 24 can best be seen in FIGS. 1, 2 and 3. As 
illustrated, the latch member 24 includes a forward nose portion 29, a 
shoulder or latching portion 30 and a rearward body portion which includes 
an opening or slot 28 (FIG. 3) for insertion of end member 26. In the 
preferred embodiment, the latch member 24 is adapted for generally arcuate 
or pivotal movement about a pivot point located in the curved portion 21 
of the latch spring between an engaged position (FIG. 6) and a disengaged 
position (FIG 7). The resulting movement of the nose portion 29 is along 
the general path of the directional arrow 31. The nose portion 29 includes 
a flat forward portion adapted for engagement with a stop member 36 (FIGS. 
6 and 8) to limit movement of the latch member 24 toward its forward or 
first position and a beveled surface 33. The surface 33 slides against a 
portion of the receptacle during insertion of the plug to depress the 
latch member 24 and allow it to engage a second latch member or shoulder 
39 of the receptacle. 
As illustrated best in FIGS. 1, 9 and 10, the forward portion 29 of the 
latch member 24 also includes a recessed portion 32 adapted for engagement 
by the elongated finger or tab portion 23. The finger or tab portion 23 
extends outwardly from the main body portion of the latch spring 19 and 
over a portion of the recessed area 32 of the latch member. The finger or 
tab portion 23 serves two functions. First, it limits the possible forward 
movement of the latch member 24 so that it does not slide off the end 
portion 26 of the latch spring. Secondly, it limits the upward movement or 
movement toward an engaged position of the latch member 24 so that such 
member can be properly inserted into the receptacle and function in the 
manner intended. In this respect, it should be noted that the latch spring 
19 is prestressed or preloaded so that the end 26 and thus the latch 
member 24 has a tendency to move upwardly to a higher rest position if the 
finger portion 23 were not present. Accordingly, this preloaded condition 
of the latch spring 19 in combination with the finger portion 23 insures 
that the latch member 24 is always in its upper or engaged position except 
when depressed for insertion or removal. 
The latch member 24 also includes a lower surface 43 which is beveled so 
that when the latch member 24 is depressed, as illustrated in FIG. 7, the 
surface 43 engages the upper surface of the spring 19. The surface 43 
extends rearwardly, at least to the point where the depression force 41 is 
exerted on the latch member 24. Accordingly, this surface 43 engaging the 
spring 19 supports the point of deflection pressure 41 during normal 
operation to prevent permanent deformation of the spring 19 as a result of 
overstressing the spring. 
Reference is next made to FIGS. 5-10 which show the structural relationship 
between the latch assembly (the latch member 24 and the latch spring 19), 
the plug member 11 and the receptacle 40. As shown best in FIG. 5, the 
latch assembly seat 16 is an elongated section which is configured to seat 
the latch spring 19. The seat portion 16 includes an elongated opening 37 
through which the tab portion 27 extends to retain the latch spring within 
the seat 16. After insertion the tab portion 27 is twisted approximately 
90.degree. to tighten the spring to the seat and to retain the same within 
the plug housing. The inside of the plug housing also includes a pair of 
posts 34 which extend through the openings 25 in the forward end 20 of the 
latch member to further secure the latch spring 19 to the plug housing. 
After insertion, the posts 34 are appropriately heat staked to permanently 
retain the latch spring therein. 
A combination stop member and guide or locking member 35 is integrally 
formed with a portion of the plug housing. As illustrated, the member 35 
extends through a cutout portion of the latch spring 19 with a portion of 
the spring positioned on each side of the member 35. In the preferred 
embodiment, this cutout portion forms the finger or tab portion 23. The 
upper portion of the member 35 is a stop member 36 adapted for engagement 
by the forward nose portion 29 of the latch member 24 for limiting the 
movement of the latch member 24 in a forward direction or direction 
opposite the latching direction. The stop member 36 also defines the first 
or forward position of the latch member 24. The lower portion of the 
member 35 includes a guide means for causing movement of and guiding the 
latch member rearwardly or toward its second position during downward 
movement of the latch member 24 toward its disengaged position. In the 
preferred embodiment, the guide means comprises a beveled portion 38 which 
is beveled downwardly as illustrated in FIGS. 5-8. The magnitude of the 
angle "A" (FIG. 8) at which the surface 38 is beveled is determined in the 
preferred structure by the swing radius or swing arc of the latch member 
24 when in its first or forward most position against the stop member 36. 
As previously described, the latch member 24 is adapted for slight arcuate 
or pivotal movement about a pivot located in the general area of the 
curved portion 21 of the latch spring. When the latch member 24 is 
disposed in its forward most position against the stop member 36, pivotal 
movement of the latch member scribes an arc "B" as shown in FIG. 8. The 
inventor has found that to achieve all of the advantages of the present 
invention, the angle "A", defined with respect to a line extending through 
the nose portion 29 of the latch member and lying perpendicular to the 
latching direction, should be greater than the swing arc "B" resulting 
from the projected pivoting of the latch member 24 when in its forward 
most position. Due to this relationship between the angle "A" and the 
swing arc "B", downward movement or depression of the latch member 24 will 
result in slight rearward movement of the same due to the engagement 
between the nose portion 29 and the beveled surface 38. If the angle "A" 
were less than the swing arc "B", downward movement of the latch member 24 
would result in no interference between the nose portion 29 and the 
beveled surface 38. On the other hand, the angle must not be so large that 
it increases the necessary releasing force to an undesirable level. For 
example, when manually depressing the latch member 24 to release the same, 
the nose portion must ride against the beveled surface. As the angle "A" 
increases, so does the releasing force. The inventor has found an angle of 
between about 5.degree. and 10.degree. and preferably about 8.degree. to 
be desirable. It is contemplated that various other structures could be 
utilized to obtain the benefits of the present invention. In these other 
structures, however, the guide means should be such that rearward movement 
of the latch member 24 in the latching direction relative to the plug 
should occur upon movement of the latch member toward its disengaged 
position. 
As shown in FIGS. 5 and 6, the latching shoulder 30 of the latch member 24 
is adapted for latching engagement with a second latch member or 
corresponding shoulder portion 39 of the receptacle 40. As can be seen, 
the latch member 24 must be depressed or moved downwardly before the plug 
can be disengaged from the receptacle. When inserted, the beveled surface 
33 contacts a portion of the receptacle and causes depression of the latch 
member for insertion into the receptacle. 
FIGS. 9 and 10 are plan views of the latch assembly of the present 
invention as installed in the plug member 11 with the latch member 24 
shown in its second or rearward most position (FIG. 9) and its first or 
forward most position (FIG. 10). 
Having described the structure of the present invention, the function and 
operation can be understood as follows. As illustrated best in FIGS. 5, 6 
and 7, the monitor plug 11 is adapted for insertion into an appropriate 
receptacle 40. Upon insertion, the beveled surface 33 of the forward nose 
portion 29 engages an edge of the shoulder member 39 resulting in rearward 
and downward movement of the latch member 24. As the plug is further 
inserted into the receptacle, the latch member 24 is depressed until the 
shoulder 39 can be cleared, allowing the plug to be fully inserted into 
the receptacle. It should be noted that during insertion of the plug 11, 
there is no engagement or interference between the nose portion 29 and the 
beveled surface 38 since the stop member 24 is in its second or rearward 
most position. When the plug is fully inserted, the latch member 24 moves 
upwardly to its engaged position in which the shoulder portions 30 and 39 
are engaged to prevent relative movement of the plug and receptacle in a 
latching direction. This upward movement results from the force supplied 
by the latch spring 19. This locks the plug member 11 within the 
receptacle. Normally, forces acting upon the plug member 11 from the 
spring contact members within the receptacle will tend to urge the plug 
member 11 toward the right as viewed in FIGS. 5-7 or in a direction out of 
engagement with the receptacle. This slight bias causes the latch member 
24 to engage the shoulder 39 and move to its first or forward most 
position relative to the plug as illustrated in FIG. 10. In this position, 
the nose portion 29 of the latch member is in close proximity with the 
stop member 36. 
It can be noted that any external forces acting on the plug 11 in the 
latching direction 13 (FIG. 5) will cause engagement between the nose 
portion 29 and the stop member 36. For example if, as often happens in the 
electronics and communications industry with respect to plugs, the plug is 
attempted to be removed by pulling on the cord or pulling on the plug 
member 11 itself without disengaging the latch mechanism, the shoulder 
portions 30 and 39 will engage and the movement of the latch member 24 
relative to the plug will be limited by the stop member 36. This has the 
effect of releasing the stresses and forces acting upon the radius portion 
of the latch spring 21. Further, even despite fairly significant forces 
tending to pull the plug from the receptacle, the latch member 24 will not 
disengage due to the beveled surface 38. As shown in FIG. 6, the beveled 
surface 38 is at an angle greater than the swing arc of the nose portion 
29. Therefore, in order for the nose portion 29 to move downwardly so as 
to release the shoulder portions 30 and 39, it must move against the 
beveled surface 38 and cause the entire latch member 24 to move rearwardly 
against the force tending to pull the plug from the receptacle. 
Accordingly, the beveled surface 38 acts as a locking angle to 
substantially increase the force necessary to pull the plug from the 
receptacle when the latch mechanism is not properly disengaged. In the 
preferred embodiment, the angle "A" is approximately 8.degree.. It has 
been found that this angle requires a disengaging force of between 20 and 
40 pounds before the latch member 24 will "cam-out" and release. When the 
latch mechanism is desired to be released, the latch member 24 is manually 
depressed at the point 41 (FIG. 5). This causes the latch member 24 to 
move downwardly to the point where the shoulder portion 30 can clear the 
shoulder 39. During this manual depression, the nose portion of the latch 
member 24 rides against the beveled surface 38. 
Although the description of the preferred embodiment has been quite 
specific, it is contemplated that various modifications could be made to 
the invention without deviating from the spirit thereof. Accordingly, it 
is intended that the scope of the present invention be dictated by the 
appended claims, rather than by the description of the preferred 
embodiment.