Racking resistant door control mechanism

A racking resistant door control mechanism for securing a pivoted door employs an elongate lock rod that extends the height of the door, is journaled for pivotal movement about a lock rod axis by door mounted bearing assemblies, and has cam type latch members welded to its opposite ends for engaging keeper members carried by upper and lower parts of a door frame. The cam and keeper members feature novel, compact arrangements of interengageable formations that are located on opposite sides of, but relatively near to, the lock rod axis of the locked door--formations that cooperate in bringing the door to its fully closed position, in securely retaining the door closed, in preventing racking movements of the closed door and its adjacent door frame, and in breaking the door open when ice formations, cold seals or the like resist initial opening movement of the door. Additional racking resistance preferably is provided by utilizing upper and lower end regions of door mounted bearing assembly covers to engage shoulders defined at junctures of the cam members with opposite ends of the lock rod, and to engage opposite end portions of at least one other lock-rod-carried component so that a plurality of lock-rod-carried components are engaged by door mounted components in a manner that is highly effective in resisting relative axial movements of the locked door, the door frame and other lock-rod-connected components.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to cam and keeper members for use in a 
racking resistant door control mechanism for securing pivoted doors of 
trucks, trailers, large cargo containers and the like, wherein the door 
control mechanism employs an elongate lock rod for extending the height of 
a pivoted door, with the cam members being connected to its upper and 
lower ends for being rotated about a pivot axis of the lock rod for 
engaging the keeper members which are connected to upper and lower parts 
of a door frame for securing the door closed. More particularly, the 
present invention relates to cam and keeper members that feature a novel, 
compact arrangement of interengageable formations that are grouped 
advantageously to extend closely about the pivot axis of a door mounted 
lock rod to cooperate in bringing the door to its fully closed position, 
in retaining the door closed, in preventing racking movements of the 
closed door and its adjacent door frame, and in breaking the door open, 
with additional racking resistance preferably being provided by utilizing 
door mounted bearing covers to engage shoulders defined at junctures of 
the cam members with opposite ends of the lock rod, and to engage opposite 
end portions of at least one other lock-rod-carried component so that a 
plurality of lock-rod-carried components are engaged by door mounted 
components in a manner that is highly effective in resisting relative 
axial movements of the locked door, the door frame and other 
lock-rod-connected components. 
2. Prior Art 
Load carrying compartments of trucks, trailer bodies and transport cargo 
containers typically use relative large single or paired sets of pivoted 
doors to provide access for loading and unloading. Because the door 
openings are large and often are defined at compartment ends by door 
frames that are not easily cross-braced and may be subject to distortion 
known as "racking," each of the pivoted doors typically is secured by a 
door control mechanism having a lock rod which extends the full height of 
the door, with the lock rod being rigidly connected at its opposite ends 
to cam type latch members configured to engage keeper members carried by 
top and bottom portions of the door frame, with mounting and operating 
components of the door control mechanism being carried by the door, and 
with various ones of these door mounted components being configured to 
cooperate with lock-rod-carried components in securing the door and in 
resisting racking movements of the closed door and its surrounding door 
frame. 
Over the years, cam and keeper proposals have been influenced by a variety 
of considerations. For example, to avoid having to provide differently 
configured cams and keepers for use at opposite ends of a lock rod (i.e., 
cams and keepers that are mirror images of each other), some proposals 
emphasize the importance of symmetrically configured cam and keeper 
designs that are "reversible" so that identical cams and identical keepers 
may be used at upper and lower ends of a lock rod. 
In seeking performance improvements, cam and keeper design proposals have 
addressed such objectives as providing enhanced racking resistance and an 
enhanced capability to resist the heavy loads that may be imposed on 
pivoted doors by shifting or shifted cargo. Cams have been proposed having 
opposed arms that each define a generally V-shaped notch configured to 
receive and cooperate with a separate, suitably configured, wedge-shaped 
keeper formation--an arrangement that has been exploited by some designs 
not only to provide strong, breakage resistant components and enhanced 
racking resistance, but also to provide cam and keeper components that 
will advantageously interact during latching so as to bring misaligned 
door and door frame portions into proper alignment. 
In order for interengaged cam and keeper formations to maintain their 
proper engagement to hold a door closed and to resist racking of the 
closed door and its door frame, abutment surfaces typically are provided 
on the cam and on the keeper--surfaces 1) that are brought into abutting 
engagement as a lock rod pivots the cam to engage the keeper to bring the 
pivoted door to its fully closed and latched position, and 2) that are 
intended to remain in engagement during the entire time that the door is 
closed and latched to aid in transferring door loading forces from the 
cams to the keepers. If such loadings as are imposed on the closed and 
latched door (e.g., due to forces generated by shifting cargo, or forces 
tending to distort the door and its door frame as a truck moves over 
uneven terrain, or the like) succeed in moving the abutment surfaces out 
of engagement, this "loosening" of the engagement between the cam and 
keeper members may defeat the capabilities of the door control mechanism 
to resist racking, to resist being damaged during use, and to maintain 
door closure so that cargo loss does not occur. 
Reasons that often aid in explaining why prior cam and keeper proposals 
have failed to maintain proper abutment surface engagement have to do with 
poor location, poor orientation, and poor configuration of such abutment 
surface portions as actually engage when a cam and keeper are fully 
latched. The location of engaging abutment surface portions (that engage 
to transmit door loading forces and the like between cam and keeper 
members when a pivoted cargo door is fully closed and latched) at a 
significant distance from the pivot axis of the locking rod can result in 
significant torque loadings being imposed on the locking rod that may tend 
to pivot the lock rod in an "unlatching" direction of movement. The closer 
that the engaging portions of the abutment surfaces can be located to the 
pivot axis of the locking rod, the less unlatching torque that will be 
generated by the same magnitude of door loading force, and the less likely 
will be the failure of the door control mechanism due to unlatching 
rotation of the locking rod. 
The orientation of the abutment surface portions that actually engage also 
is important, for inappropriate orientation of the plane of engagement can 
cause "normal" and "tangential" components of the force that is being 
transmitted from a cam to a keeper to interact in such a way as to cause 
unlatching rotation or other undesired movement of the locking rod that 
may, in turn, cause the cam to release its latching engagement with the 
keeper. Many prior proposals have neglected to take properly into account 
the important role that abutment surface location and orientation can play 
in determining how a particular cam and keeper configuration will perform. 
Still another aspect of cam and keeper engagement that needs to be taken 
properly into account is the configuration of such abutting surface 
portions as actually engage when the cam and keeper are latched. Previous 
proposals typically have called for the abutment surface portions that 
actually engage to be defined by different radii of curvature--an 
arrangement that has severely limited the size of the surface area wherein 
the cam and keeper abutment surfaces actually engage. By minimizing the 
size of the surface area wherein the abutment surfaces actually engage, 
the magnitude of the force that must be transmitted per unit of surface 
area is caused to be quite high--often calling for many thousands of 
pounds of force to be transmitted between engaging cam and keeper surface 
areas that measure considerably less than a square inch in size. These 
force-concentrated loadings imposed on cam and keeper members can cause 
structural failures that are far less likely to occur if the same loadings 
are distributed across engagement surface areas of greater size. 
A significant drawback common to many previously proposed cam and keeper 
configurations is their overall size. As doors have increased in size 
while door frames have diminished in size (to meet present day needs that 
call for access openings of maximum size to be provided in cargo carrying 
compartments that are of strictly limited exterior dimension), it has 
become increasingly important for cam and keeper components to exhibit 
narrow profiles and to occupy only a minimum of space--and to do these 
things without unduly limiting their capability to perform latching and 
closure retaining functions, and to exhibit good racking resistance in the 
presence of severe door loadings. Many previously proposed cam and keeper 
configurations do not offer the combination of maximized performance and 
minimized size that is required to meet present day needs. 
A need not specifically addressed by many cam and keeper proposals is the 
provision of cam and keeper surfaces that are intended to engage during 
unlatching to break open a closed door that initially may tend to resist 
opening due to a buildup of ice around door and door frame junctures, due 
to seals that have become relatively rigid in a cold environment, due to a 
difference in air pressure on opposite sides of the door, etc.--which 
tendency frequently is encountered with the tightly fitting, seal carrying 
doors of refrigerated trucks and the like. In efforts to provide cam and 
keeper configurations that are of narrow profile and small size, and that 
offer a high degree of racking resistance as well as an ability to 
maintain door closure in the presence of severe door loadings, the 
desirability of also incorporating into cam and keeper designs an 
interaction capability to break open stubborn doors often has fallen by 
the wayside. 
3. The Referenced "First and Second Parent Cases" 
The referenced First Parent Case addresses the need to provide enhanced 
racking resistance in a door control mechanism by utilizing door mounted 
components and lock-rod-carried components that feature an advantageous 
series of engagements. All but two of the engaging door mounted and 
lock-rod-carried components are arranged "in series engagement" so that a 
maximum number of racking resistant engagements are defined by a minimum 
number of components. In preferred practice, the present invention 
utilizes the "in series engagement" arrangement of door control mechanism 
components that forms the subject of the First Parent Case, the disclosure 
of which is incorporated herein by reference. 
The referenced Second Parent Case addresses the need to provide ferrous 
metal components of a door control mechanism with good corrosion 
resistance--it being noted that the normal operating environment in which 
cargo containers, freight hauling trucks and the like are employed may 
frequently expose door control mechanism components to inclement weather 
as well as salt spray and other conditions or substances that tend to 
promote corrosion. In preferred practice, the present invention utilizes 
cams, keepers and other door control mechanism components that have had 
their exposed surfaces protected utilizing features of the proposal that 
forms the subject of the Second Parent Case, the disclosure of which is 
incorporated herein by reference. 
SUMMARY OF THE INVENTION 
The present invention addresses the foregoing and other needs, 
considerations and drawbacks of the prior art by providing cam and keeper 
members of novel and improved configuration that utilize a compact 
arrangement of interengageable formations to provide a racking resistant 
door control mechanism for securing a pivoted door of a cargo vehicle or 
container having an elongate lock rod that extends the height of the door, 
that is journaled for pivotal movement about a lock rod axis by door 
mounted bearing assemblies, and that deploys the cam type latch members by 
connecting them to opposite ends of the lock rod for latchingly engaging 
the keeper members which are connected to upper and lower parts of a door 
frame. 
One feature of cams and keepers that embody the preferred practice of the 
present invention resides in their being of relatively small size and 
presenting a relatively narrow profile to comply with present day 
requirements without sacrificing the important capabilities of these 
members, when fully latched, to transmit relatively high force loadings 
therebetween, to resist racking, and to exhibit desirably lengthy service 
lives. 
Another feature of preferred practice resides in the employment of cam and 
keeper abutment surfaces that are located, oriented and configured in a 
manner that tends not to unlatch, pull apart, deform or break--an 
arrangement that has been proved in tests of high loading forces applied 
to cargo doors to remain latched and to remain serviceable when many other 
cam and keeper configurations employed in present-day service have been 
found to fail. Engaged abutment surfaces are located in unusually close 
proximity to the locking rod pivot axis, are oriented to extend nearly 
parallel to the plane of the door they hold closed, and are configured to 
provide relatively large, relatively flat surface areas of engagement to 
avoid the generation of stress concentrations. 
In preferred practice, an enlarged head formation that defines the keeper's 
abutment surface has an end portion that extends unusually close to the 
pivot axis of the cam--to a location that overlies a space in which a 
central portion of the cam resides when the cam and keeper are fully 
latchingly engaged. To accommodate the end portion of the keeper (the 
presence of which otherwise would interfere with movement of the cam into 
and out of engagement with the keeper), a U-shaped recess is formed in the 
cam to receive and to "wrap about" the keeper end portion during latching 
and unlatching movements of the cam and the keeper. 
In preferred practice, a cam and keeper are provided with interfitting 
formations that cooperate in bringing the door to its fully closed 
position, in securely retaining the door closed even when the door is 
subjected to relatively high cargo imposed loadings, in preventing racking 
movements of the closed door and its adjacent door frame, and in breaking 
the door open when ice formations, cold seals or the like resist initial 
opening movement of the door. Two opposed cam arms that carry V-shaped 
notches engage separate, spaced keeper posts of wedge-shaped cross-section 
to axially align the cams and keepers during latching, and to oppose 
racking forces when latched. Recognition is taken of the fact that, as the 
two arms of the cam rotate into and out of engagement with the keeper, 
only one of the arms carries out 1) the bulk of the alignment effort, 2) 
the bulk of the door closing effort, and 3) the bulk of the door opening 
effort. This "primary" arm is given greater length than the "secondary" 
arm, is provided with a V-shaped notch that is of greater length that is 
the notch formed in the "secondary" arm, and is provided with a more 
gentle notch taper than is used with the notch of the "secondary" arm; and 
corresponding improvements are made in such portions of the keeper as 
interact with the "primary" arm--the result being to provide a smooth 
acting, easy to operate door control mechanism that puts to good use the 
limited space occupied by its components. 
In providing anti-racking capabilities, two undesirable types of relative 
movement (in a direction extending axially along the lock rod of a door 
control mechanism) are to be inhibited and held to a minimum. Providing 
improved double-wedge-acting cams and keepers that tend to maintain fully 
latched engagement (i.e., cams and keepers that incorporate the 
improvements disclosed herein) deals with one of these undesired types of 
movement, namely movement that may tend to occur between a locking rod and 
keeper-carrying upper and lower portions of a door frame. Providing 
lock-rod-carried and door connected components that engage in advantageous 
ways (in accordance with features of the invention of the First Parent 
Case) deals with the other of these undesired types of movement, namely 
movement that may tend to occur between a locking rod and the door 
portions on which it is pivotally mounted. In most preferred practice, the 
present invention utilizes its improved cam and keeper features in 
combination with the improvements of the First Parent Case to provide a 
door control mechanism that offers the fullest possible scope of racking 
resistance. 
More particularly, the cams and keepers of the present invention preferably 
are used with door control mechanism components that are arranged in the 
manner that is described in the referenced First Parent Case to provide 
enhanced racking resistance by positioning upper and lower end regions of 
door mounted bearing assembly covers 1) to engage shoulders defined at 
junctures of the cam members with opposite ends of the lock rod, and 2) to 
engage opposite end portions of at least one other lock-rod-carried 
component so that a plurality of lock-rod-carried components are engaged 
by door mounted components in a manner that is highly effective in 
resisting relative axial movements of the locked door, the door frame and 
the components of the door control system. 
In preferred practice, a racking resistant door control mechanism employs 
an elongate lock rod that extends the height of a door on which the lock 
rod is mounted, with the lock rod being journaled for pivotal movement 
about a pivot axis that extends centrally along the length of the lock rod 
by bearing assemblies having steel covers that are connected by fasteners 
to the door. The lock rod has upper and lower cam type latch members (that 
embody improvement features of the type described above) connected to its 
opposite ends for engaging keeper members carried by upper and lower parts 
of a door frame for holding the door closed. The lock rod also extends 
through and is welded to a steel sleeve at a location spaced a short 
distance upwardly from the location of the lower latch member. The steel 
sleeve and the steel bearing covers are configured and positioned such 
that the steel bearing covers are held in engagement 1) with the cam type 
latch members, and 2) with opposite ends of the sleeve, to thereby provide 
a high degree of resistance to axial movement of the lock rod relative to 
the door on which it is mounted. 
In preferred practice, the steel sleeve has a bottom surface that faces 
downwardly toward an upwardly facing surface of the bottom cam member, and 
a bottom bearing cover has a height that is received in a slip fit so as 
to be closely sandwiched between these downwardly and upwardly facing 
surfaces--a construction that, in and of itself, serves to prevent axial 
movement of the lock rod relative to the door to which the bottom bearing 
cover is bolted. 
In preferred practice, the steel sleeve has upwardly and downwardly facing 
surfaces at its opposite ends, and is sandwiched in a slip fit between the 
relatively large bottom bearing cover and a relatively smaller strap-like 
bearing cover that is bolted to the door just atop the sleeve--a 
construction that also, in and of itself, serves to prevent axial movement 
of the lock rod relative to the door to which the bottom bearing cover is 
bolted. 
In preferred practice, the two construction arrangements just described, 
each of which serves independently to block both upward and downward axial 
movements of the lock rod relative to the door on which it is mounted, are 
used in combination with still another construction that also serves to 
prevent axial movement of the lock rod. This third construction utilizes 
engagement between a bottom surface of the bottom bearing cover and an 
upwardly facing surface of the bottom cam member (which blocks upward 
movement of the lock rod relative to the door), and between a top surface 
of the top bearing cover and a downwardly facing surface of the upper 
latch member (which blocks downward movement of the lock rod relative to 
the door). 
Also, in preferred practice, the advantageously configured cams and keepers 
of the present invention (and other components of the door control 
mechanism with which the cams and keepers are used) have their exposed 
ferrous metal surfaces provided with corrosion resistance in accordance 
with the approach that is described in the referenced Second Parent Case. 
The various metal components of the door control mechanism including the 
steel sleeve and the steel bearing covers are protectively coated before 
being welded or otherwise assembled. Some rigid connections between 
components of the lock rod assembly preferably are formed by utilizing 
normally hidden welds of relatively small size that burn through the 
protective coatings and are, in turn, protectively coated by a zinc rich, 
polymer containing film applied as a "touch-up" spray that matches the 
appearances of the corrosion resistant coatings applied to the various 
metal components.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIGS. 1-3, a door control mechanism that embodies the 
preferred practice of the present invention is indicated generally by the 
numeral 100. Because a majority of the components of the door control 
mechanism 100 are identical to components of door control mechanisms that 
are described in the referenced Parent Cases, features that are shared by 
the door control mechanism 100 and the door control mechanisms of the 
Parent Cases will be described before turning to a detailed description of 
unique features of cam type latch members 130, 140 and keeper members, 
230, 240--features that differentiate the door control mechanism 100 from 
the door control mechanisms that are described in the Parent Cases. 
Shown in FIG. 1 are upper and lower frame portions of a load carrying 
compartment of a truck body; a trailer body, or a cargo container, which 
are designated by the numerals 30, 40, respectively. Defined between the 
upper and lower door frame portions 30, 40 is a door opening, indicated 
generally by the numeral 50. A door 60 is shown in closed 
position--wherein the door 60 closes at least a significant portion of, if 
not the entirety of, the door opening 50. 
In a manner well understood by those who are skilled in the art, the door 
60 is hinge-mounted for pivotal movement about a vertically extending axis 
(not shown) that is located a suitable distance to one side of the 
depicted door control mechanism 100 (i.e., rightwardly with respect to 
what is depicted in FIG. 1) so that the door 60 can pivot between an open 
position (not shown) and the fully closed and latched position that is 
depicted in FIG. 1. 
Referring to FIGS. 1-3, the door control mechanism 100 includes a welded 
lock rod assembly that is indicated generally by the numeral 110. The 
assembly 110 includes an elongate tubular lock rod 120 that has upper and 
lower end regions 122, 124 (see FIG. 3). An upper cam type latch member 
130 and a lower cam type latch member 140 (which have configurations that 
are mirror images of each other, as will be seen by comparing the more 
detailed depictions of these components provided by FIGS. 8 and 9, 
respectively) are connected to the upper and lower end regions 122, 124, 
respectively. A steel sleeve 150 (of slightly greater inner diameter than 
is the outer diameter of the tubular lock rod 120) is slip-fit onto the 
lock rod 120 and is welded in place at a location spaced a short distance 
upwardly from the lower latch member 140. 
As is shown in FIGS. 3, 8 and 9, the latch members 130, 140 have stem 
portions 131, 141 that are configured to extend into the tubular interiors 
of the upper and lower end regions 122, 124 of the lock rod 120 so that 
the latch members 130, 140 will have a mechanical connection to the lock 
rod 120 that can be secured as by welding. Circumferentially extending 
flanges 133, 143 of the latch members 130, 140 overlie and underlie the 
upper and lower end regions 122, 124, respectively. More specifically, the 
flange 133 has upper and lower shoulders 132, 134, with the lower shoulder 
134 overlying the upper end region 122 of the lock rod 120; and, the 
flange 143 has upper and lower shoulders 142, 144, with the upper shoulder 
142 underlying the lower end region 124 of the lock rod 120. 
Referring to FIG. 1, the door control mechanism 100 also includes upper and 
lower keeper members 230, 240 that are configured to receive and 
cooperatively engage the cam type latch members 130, 140, respectively, in 
closing the door 60, in latching and retaining the door 60 closed, in 
resisting racking of the door 60 and its surrounding door frame (upper and 
lower portions of which are designated by the numerals 30 and 40), and in 
breaking the door 60 open. These and other features and characteristics of 
the interaction of the cam and keeper members 130, 140 and 230, 240 will 
be described in greater detail later herein. 
The lock rod 120 preferably is formed from seam-welded steel tubing that 
preferably has been corrosion protection coated by its manufacturer, for 
example by applying a zinc/chromate/polymer coating thereto under optimal 
conditions that permit a high quality corrosion resistant finish to be 
applied, usually at a time before the newly manufactured tubing has been 
cut to length. A process by which steel tubing can be galvanized to 
provide a high quality zinc coating is described in expired U.S. Pat. No. 
3,927,816. A process by which a chromate conversion coating followed by an 
application of clear organic coating such as a thermosetting polymer can 
be applied to zinc plated tubing is described in expired U.S. Pat. No. 
3,790,355. Other commercially practiced protective coating processes that 
provide zinc/chromate/polymer coatings also can be used. 
Referring to FIG. 3, the lock rod 120 may be defined by a single, 
full-length tubular member, or may be defined by two shorter tubular 
members that are arranged end-to-end and rigidly connected to thereby 
provide a full length lock rod. The reference numeral 120 refers to the 
entire length of the lock rod--which extends from the upper end region 122 
to the lower end region 124. If two lock rod elements are to be used to 
define a full length lock rod 120, they have lengths that are selected so 
that their end-to-end juncture is located centrally within the confines of 
the steel sleeve 150. 
Because the door control mechanism 100 will not differ in appearance 
regardless of whether a single, full length steel tube is used to form the 
lock rod 120 or whether the lock rod 120 is formed from two shorter 
tubular elements, there is no need to provide a separate set of drawing 
views to distinguish the appearances of one-element and two-element lock 
rods. Therefore, in FIG. 3, the numeral 120U can be thought of as 
designating either upper portions of a one-element lock rod or an upper of 
element of a two-element lock rod (which extends upwardly from centrally 
within the sleeve 150 to the downwardly facing shoulder 134 of the upper 
latch member 130); and, the numeral 120L can be thought of as designating 
either lower portions of a one-element lock rod or a lower element of a 
two-element lock rod (which extends downwardly from centrally within the 
sleeve 150 to the upwardly facing shoulder 142 of the the lower latch 
member 140). 
Referring to FIGS. 1-3 and 7, the sleeve 150 has an upwardly facing end 
surface 152 and a downwardly facing end surface 154. Referring to FIG. 7, 
a pair of axially spaced, identically configured, elongate slots 156, 158 
are formed through the back side of the sleeve 150 for providing locations 
where welds can be formed to securely connect the sleeve 150 to the lock 
rod 120. For example, an elongate weld 159 is formed within the confines 
of the slot 158 (substantially filling the slot 158) to connect the sleeve 
150 to the lower lock rod portion 120L; and, an identical elongate weld 
(not shown) normally is formed within the confines of the slot 156 to 
connect the sleeve 150 to the upper lock rod portion 120U (once a lower 
end of the upper lock rod portion 120U has been inserted half-way down 
into the sleeve 150 to abuttingly engage in end-to-end relationship the 
upper end of the lower lock rod portion 120L which is depicted in phantom 
in FIG. 7). 
If the lock rod 120 is formed from a single, full-length reach of steel 
tubing, the weld 159 formed in the slot 158, and the identical weld (not 
shown) formed in the slot 156 will securely connect the sleeve 150 to the 
one-piece lock rod 120. If the lock rod 120 is formed from separate lower 
and upper lengths of tubing 120L, 120U, respectively, the described welds 
will enable the welded-in-place sleeve 150 to provide a secure connection 
between the lower and upper lock rod elements 120L, 120U. 
Referring to FIGS. 1, 3 and 7, a U-shaped handle mounting bracket 160 is 
welded to the outside surface of the sleeve 150. The bracket 160 provides 
a mount that supports an elongate operating handle 170 (see FIG. 1) that 
is used to apply force to the lock rod 120 to pivot the lock rod 120, 
whereby the lock rod 120, in turn, correspondingly pivots the upper and 
lower latch members 130, 140. A fastener 172 extends through a hole 162 
(see FIG. 7) formed in the bracket 160 and through an aligned hole (not 
shown) formed in one end region of the handle 170 to connect the handle 
170 to the bracket 160. A handle retainer assembly 175 (see FIG. 1) of 
conventional form is mounted on the door 60 for receiving and releasably 
retaining the handle 170 to secure the door closure mechanism 100 in the 
locked position depicted in FIG. 1--wherein the door control mechanism 
100, in turn, secures the door 60 closed. 
Referring to FIGS. 1-3, four bearing assemblies 410, 420, 430, 440 are 
mounted on the door 60 and serve to journal the lock rod 120 for pivotal 
movement about an imaginary pivot axis 101 that extends centrally along 
the length of the lock rod 120. The bearing assemblies have stamped steel 
covers 310, 320, 330, 340, respectively. The bearing assemblies 410, 420 
are located between the upper bearing assembly 430 and the lower bearing 
assembly 440. 
The bearing assembly 410 has a stamped, strap-like steel cover 310 that 
defines upper and lower surfaces 312, 314, respectively, and that is 
connected to the door 60 by two bolts 315. The bearing assembly 420 has a 
stamped, strap-like steel cover 320 that defines upper and lower surfaces 
322, 324, respectively, and is connected to the door 60 by four of bolts 
325. The upper bearing assembly 430 has a complexly configured, stamped 
steel cover 330 that defines upper and lower surfaces 332, 334, 
respectively, and that is connected to the door 60 by four bolts 335. The 
lower bearing assembly 440 has a stamped steel cover 340 that is identical 
to the upper cover 330 but is inverted, that defines upper and lower 
surfaces 342, 344, respectively, and that is connected to the door 80 by 
four bolts 345. 
The positioning of the bearing assembly 410 is not especially critical 
inasmuch as the purpose principally served by the bearing assembly 410 is 
that of stabilizing the lock rod 120 at a location generally mid-way 
between the bearing assemblies 420, 430 to ensure that the lock rod 120 
does not deflect from its center axis 101, and to ensure that portions of 
the door 60 that are connected to the lock rod 120 by the bearing assembly 
410 do not move relative to each other. The positioning of the bearing 
assemblies 420, 430, 440, on the other hand, is of some importance 
inasmuch as certain racking resistant features of the door control 
mechanism 100 derive, in part, from ensuring that the bearing covers 320, 
330, 340 are properly positioned. 
To enhance the racking resistance of a rod lock type of door control 
mechanism, there are two types of relative movements that one can try to 
prevent. One is relative movement between the lock rod 120 and the upper 
and lower door frame portions 30, 40. Preventing this type of relative 
movement depends in large measure on the character and success of the 
interaction that takes place between the upper cam and keeper members 130, 
230, and the interaction that takes place between the lower cam and keeper 
members 140, 240--a subject that will be treated later herein in 
conjunction with a more detailed description of the configuration and 
operation of the cam and keeper members 130, 140 and 230, 240. 
The other type of movement that one seeks to prevent is relative movement 
between the lock rod 120 and the door 60--a subject that is dealt with in 
some detail in the referenced First Parent Case, and also is dealt with 
next in the present document inasmuch as the door control mechanism 100 
preferably utilizes these racking resistant features in combination with 
cam and keeper features (described later herein) to deal effectively with 
both of these undesirable types of racking movements. If the cam and 
keeper members 130, 140 and 230, 240 can function well in preventing 
relative axial movement between the lock rod 120 and the door frame 
portions 30, 40, and if the racking resistant features that are about to 
be described can function well in preventing relative axial movement 
between the lock rod 120 and the door 60, the net effect is to provide 
good racking resistance that will successfully oppose relative movements 
between the door frame portions 30, 40 and the door 60. 
In accordance with features that form the subject of the First Parent Case, 
relative movement between the lock rod 120 and the door 60 are sought to 
be prevented by utilizing a set of "in series engagements" between 
lock-rod-connected components and door connected components, with correct 
positioning of the bearing covers 320, 330 and 340 being of importance in 
carrying out this objective. 
By way of a first example, the sleeve 150 is sandwiched between the bearing 
covers 320, 340, with the top surface 152 of the sleeve 150 engaging the 
bottom surface 324 of the cover 320, and with the bottom surface 154 of 
the sleeve 150 engaging the top surface 342 of the cover 340--which 
arrangement constitutes a first paired set of surface engagements (i.e., a 
first bearing-cover-related arrangement of paired surface engagements) 
that is utilized by the door control mechanism 100 to prevent both 
relative upward and relative downward axial movements of the lock rod 120 
with respect to the door 60. Stated in another way, the sandwiching of the 
sleeve 150 by the bearing covers 320, 340 is the first of three racking 
resistant features relied upon, in combination, by the door control 
mechanism 100 to prevent relative axial movement of door connected and 
lock-rod-connected components. 
By way of a second example, the lower bearing cover 340 is sandwiched 
between the sleeve 150 and the lower latch member 140, with the top 
surface 342 of the lower bearing cover 340 engaging the bottom surface 154 
of the sleeve, and with the bottom surface 344 of the lower bearing cover 
140 engaging the top surface 142 of the lower latch member 140--which 
arrangement constitutes a second paired set of surface engagements (i.e., 
a second bearing-cover-related arrangement of paired surface engagements) 
that is utilized by the door control mechanism 100 to prevent both 
relative upward and relative downward axial movements of the lock rod 120 
with respect to the door 60. Stated in another way, the sandwiching of the 
lower bearing cover 340 by the members 140, 150 is the second of three 
racking resistant features relied upon, in combination, by the door 
control mechanism 100 to prevent relative axial movement of door connected 
and lock-rod-connected components. 
By way of a third example, the upper bearing cover 330 has an upper surface 
332 which is held in engagement with the lower surface 134 of the upper 
cam member 130, and the lower bearing cover 340 has a lower surface 344 
that is held in engagement with the upper surface 142 of the lower cam 
member 140--which arrangement constitutes a third paired set of surface 
engagements (i.e., a third bearing-cover-related arrangement of paired 
surface engagements) that is utilized by the door control mechanism 100 to 
prevent both relative upward and relative downward axial movements of the 
lock rod 120 with respect to the door 60. Stated in another way, the 
sandwiching of the door-interconnected upper and lower bearing covers 330, 
340 by the flanges 133, 143 of the upper and lower cam members 130, 140 is 
the third of three racking resistant features relied upon, in combination, 
by the door control mechanism 100 to prevent relative axial movement of 
door connected and lock-rod-connected components. 
Looking more closely at the limited number of components that are employed 
in defining all three of the above described paired sets of racking 
resistant features, it will be seen that, only three lock-rod-carried 
elements (namely the cam members 130, 140 and the sleeve 150) and only 
three door-carried elements (namely the bearing covers 320, 330, 340) are 
utilized in forming all three of the described "sandwichings" of 
components. The use of so few components to achieve rather a lot of 
anti-racking capability is possible due to the in-series, in-line 
positioning of four of the essential elements, namely the lower cam member 
140, the lower bearing cover 340, the sleeve 150 and the bearing cover 
320--which are arranged in series in engagement one-with-the-next, with no 
intermediate spaces interposed between any two adjacent pairs of these 
four elements. 
This is an unusually economical approach that maximizes the use that can be 
made of a limited set of simple components to achieve a powerful degree of 
"anti-racking" capability, and largely boils down to a matter of providing 
the lock rod with a double-ended sleeve 150, and then utilizing the sleeve 
150 and the cam members 130, 140 to provide racking resistance by 
strategically positioning the three bearing covers 320, 330, 340 to engage 
the lock-rod-carried members 130, 140, 150. 
Additional features of the door control mechanism 100 that also are brought 
out in the referenced Parent Cases reside in the use that is made by each 
of the bearing assemblies 410, 420, 430, 440 of plastic bearing liners 
(indicated generally by the numeral 500 in FIGS. 4 and 5) that feature 
some novel points of design. To begin with, while the bearing covers 310, 
320, 330, 340 may differ one from another in configuration, identically 
configured enlarged regions 317, 327, 337, 347 are defined by the bearing 
covers 310, 320, 330, 340 so that identically configured plastic bearing 
liners 500 can be housed by the enlarged regions 317, 327, 337, 347. 
Referring to FIGS. 4 and 5, each of the bearing liners 500 includes a pair 
of components that mate when assembled to provide lock rod bearings of 
good integrity. A plate-like component 510 that is of generally 
rectangular shape except that its corners 512 are generously rounded. A 
U-shaped component 520 has opposed leg portions 522 that are 
interconnected by a C-shaped portion 524. Projections 526 of generally 
rectangular cross-section are carried at the distal ends of the leg 
portions 522, and are configured to be snugly received with generally 
rectangular openings 516 (see FIGS. 5 and 6) formed in the plate-like 
component 510. A sizable arcuate surface 514 is defined by the plate-like 
component 510 and is located between the openings 516. 
Referring to FIG. 6 wherein one of the liners 500 is shown in cross-section 
housed within the enlarged region 317 of the bearing cover 310, arcuate 
surface 514 and the C-shaped portion 524 have radii of curvature that 
match the outer diameter of the lock rod 120--thereby enabling the surface 
514 and the C-shaped portion 524 to engage opposite sides of the lock rod 
120 so as to confine the rotation of the lock rod to an axis (not shown) 
that is centered between the arcuate surface 514 and the inner face of the 
C-shaped portion 524. 
A feature of the bearing liner assembly 500 that is best seen in FIG. 6 is 
that vertical passages, indicated generally by the numerals 550, are 
provided near junctures of the arcuate surface 514 with the leg portions 
522. The vertical passages 550 aid in ducting foreign matter downwardly 
for discharge from the bearing assemblies 410, 420, 430, 440, and thereby 
help to ensure that the bearing assemblies 410, 420, 430, 440 smoothly 
journal the lock rod 120 for a service life of good longevity. 
Four "corner" mounting holes 565, and two "center" mounting holes 555 are 
formed through the plate-like component 510. The four corner holes 565 
receive the four bolts 325 that are used to bolt the bearing cover 320 to 
the door 60. The two center holes 555 receive the two bolts 315 that are 
used to bolt the bearing cover 310 to the door 60. The cover 320 employs a 
total of four bolts 325 because it is an "anti-racking" component (as is 
described above) that may be axially loaded in the presence of forces that 
tend to cause racking. The cover 310 employs only the two bolts 315 
because it is not subjected to axial loadings and does not perform an 
"anti-racking" function. 
In preferred practice, the rear and front components 310, 320 are formed 
from a substantially rigid, strong, crack resistant plastics material 
using extrusion molding techniques. Because door control assemblies need 
to operate smoothly in ambient temperatures typically extending from below 
zero degrees Fahrenheit (and sometimes in the presence of severe ice 
buildup) to above one hundred degrees Fahrenheit, selection of a plastics 
material that is serviceable in a wide range of temperatures and that 
resists "freeze up" during cold winter days is desirable. As those who are 
skilled in the art will readily understand, a variety of plastics 
materials suitable for this purpose are commercially available. An acetal 
resin sold by E.I. DuPont deNemours & Co., Wilmington, Del. 19898 under 
the registered trademark "DELRIN 500" is, for example, a good commercially 
available choice. 
In preferred practice, the door control mechanism 100 preferably is 
provided with a desired degree of corrosion resistance by 1) protectively 
coating the lock rod 120 (or the upper and lower components 120U, 120L 
that are to be assembled to form the lock rod 120) prior to cutting the 
lock rod to length, and prior to welding and to the carrying out of other 
significant assembly effort, with the application of protective coating 
being carried out under optimal conditions, preferably in the facility of 
the manufacturer of the rod, and preferably utilizing what has been 
described herein as a zinc/chromate/polymer coating; 2) protectively 
coating the latch members 130, 140 and the steel sleeve 150 separately, 
preferably also under optimal conditions, also at a time prior to 
assembly; 3) welding the cam members 130, 140 to the lock rod 120 
utilizing small elongate welds located so that they normally are hidden; 
and, 4) applying touch-up spray of the type described previously to form a 
zinc-rich polymer containing film in limited areas where metal surface was 
exposed when the lock rod was cut to length, and in limited areas where 
the elongate welds were formed, with the touch-up coating being of a type 
that matches as closely as possible the finished appearance of other 
corrosion resistant coating applied to adjacent surface areas. 
Much of what has been described above forms the subject matter of the 
referenced Parent Cases, with the First Parent Case having to do with the 
anti-racking capabilities that derive from the described positioning of 
door connected and lock-rod-carried components to minimize relative 
movements between the lock rod 120 and the door 60, and with the Second 
Parent Case having to do with provision of the described corrosion 
resistant features--all of which preferably are utilized in conjunction 
with features of the cam members 130, 140 and the keeper members 230, 240 
that now will be described. 
As a starting point, the cam members 130, 140 have features of "similarity" 
and "symmetry" that should be noted; and, the keeper members 230, 240 have 
features of "symmetry" and "identity" that also should be taken into 
account. 
Referring to FIGS. 8, 9 and 10, the cam members 130, 140 are similar in 
that they have configurations that are top-to-bottom mirror image 
reversals of each other. The cam members 130, 140 also have body portions 
600 that are symmetrical about an imaginary center plane, which plane is 
designated (for the cam 140) by the numeral 601 in FIG. 10. Stated in 
another way, if the cam members 130, 140 did not have stem portions 131, 
141 that extend away from the body portions 600 along the axis 101, the 
cam member 140 would be completely symmetrical about the center plane 601 
and would, in fact, be completely identical to the cam member 130. Thus, 
the cam member bodies 600 are identical one with another, and each is 
symmetrical about its center plane (such as the center plane 601 shown in 
FIG. 10); the cam member stems 131, 141 are mirror image reversals of each 
other; and, one way of looking at the only real difference that exists 
between the cam members 130, 140 is to note that the cam members 130, 140 
are identical except that the cam member 130 has its stem portion 131 
extending downwardly from its body 600, whereas the cam member 140 has its 
stem portion 141 extending upwardly from its body 600. 
Referring to FIGURE to FIGS. 8, 9 and 11, the keeper members 230, 240 have 
bodies 700 that are symmetrical about an imaginary center plane, which 
plane is designated (for the cam 240) by the numeral 701 in FIG. 11. While 
one could observe that the keeper members 230, 240 (like the cam members 
130, 140) are "top-to-bottom mirror image reversals" of each other, one 
can observe more simply that the keeper members 230, 240 have 
configurations that are, in fact, completely identical one with another. 
Referring to FIGS. 8-11, each of the cam members bodies 600 has a central 
portion 610 that is intersected by the pivot axis 101, with a relatively 
long arm 620 and a relatively short arm 640 extending in generally 
opposite directions from the central portion 610. Stated in another way, 
the long arm 620 and the short arm 640 extend in generally opposite 
directions relative to the axis 101. The long and short arms 620, 640 
define separate long and short V-shaped notches 622, 642, respectively, 
that open as they extend generally away from the axis 101. As is best seen 
in FIG. 10, the long V-shaped notch 622 has its opposite sides defined by 
primary engagement surfaces 630 that are relatively gently inclined 
relative to the plane 601 at angles 631 of about fifteen degrees. The 
short V-shaped notch 642 has its opposite sides defined by secondary 
engagement surfaces 650 that are more steeply inclined relative to the 
plane 601 at angles 651 of about twenty-five degrees. 
Referring to FIGS. 8 and 10 where front portions of one of the cam bodies 
600 are depicted, to FIG. 7 wherein rear portions of one of the cam bodies 
600 is depicted, and to FIG. 12 wherein portions of one of the cam bodies 
600 is shown as viewed "on end," the long arm 620 has a generally flat 
front and rear surface portions 625, 626 that are inclined relatively to 
each other to define a wedge shape that narrows as the front and rear 
surface portions 625, 626 extend toward and are are joined by rounded end 
surface portions 629; the short arm 640 has generally flat front and rear 
surface portions 645, 646 that are inclined relatively to each other to 
define a wedge shape that narrows as the front and rear surface portions 
645, 646 extend toward and are are joined by rounded end surface portions 
649; a vertically extending U-shaped recess 660 is provided at the 
junctures of the front surface portions 625, 645; and relatively flat back 
wall portions 662 join the rear surface portions 626, 646. Referring to 
FIGS. 10 and 12, the U-shaped recess 660 is offset slightly toward the 
long-arm side of the pivot axis 101. 
Referring to FIGS. 8, 9, 11 and 12, each of the keeper bodies 700 has a 
"base" that is defined by a relatively thin, elongate rear wall 710 having 
relatively flat front and rear surfaces 712, 714. As is best seen in FIGS. 
12 and 13, the flat front and rear surfaces 712, 714 of the rear wall 710 
(of the base of each of the keeper bodies 700) substantially parallel each 
other--and, the thin, flat, elongate rear wall 710 (of the base of each of 
the keeper bodies 700) can be thought of as defining a so-called "base 
plane" of the associated keeper body 700. The rear wall 710 is of 
generally rectangular shape except that, about midway along its length, 
opposite edges of the rear wall have inset portions 716 (best seen in 
FIGS. 8 and 11) that provide locations where welds may be formed (not 
shown) for connecting the keeper body 700 to one of the door frame 
portions 30, 40 (depicted only in FIG. 1). 
Referring to FIG. 11, two spaced posts 720, 740 extend forwardly from 
opposite end regions of the rear wall 710. The posts 720, 740 are of 
generally wedge-shaped cross-section (i.e., they each have a generally 
triangular cross section) defined, in part, by inclined primary engagement 
surfaces 730 that are located on opposite sides of the post 720, and by 
inclined secondary engagement surfaces 750 that are located on opposite 
sides of the post 740. The primary engagement surfaces 730 extend 
symmetrically about the center plane 701 at relatively gentle angles of 
inclination 731 that are selected to match the fifteen degree angles of 
inclination 631 of the primary engagement surfaces 630 of the cam body 600 
(depicted in FIG. 10). The secondary engagement surfaces 750 extend 
symmetrically about the center plane 701 at relatively steeper angles of 
inclination 751 that are selected to match the twenty-five degree angles 
of inclination 651 of the secondary engagement surfaces 650 of the cam 
body 600 (depicted in FIG. 10). 
Continuing to refer to FIG. 11, the primary engagement surfaces 730 are 
joined by a rounded inner end surface 727, and by a generally flat (or 
only slightly curved) outer end surface 729. Similarly, the secondary 
engagement surfaces 750 are joined by a rounded inner end surface 747, and 
by a generally flat (or only slightly curved) outer end surface 749. 
Referring to FIG. 12, the rounded inner end surface 727 executes a 
relatively large radius curve 728 to join with the front surface 712 of 
the rear wall 710; and, the rounded inner end surface 747 executes a 
relatively small radius curve 748 to join with the front surface 712. The 
spacing between the inner end surfaces 727, 747 is selected such that the 
inner end surfaces 727, 747 can be received in narrow rounded end regions 
627, 647 (see FIG. 10) of the V-shaped notches 622, 642 during movements 
of the cam body 600 into and out of latching engagement with the keeper 
body 700, which movements will be described shortly in conjunction with a 
discussion of FIGS. 12-15. 
Referring to FIG. 8, wedge-shaped formations 741 are defined along opposite 
sides of the post 740 where the post 740 joins with the rear wall 710. The 
wedge-shaped formations 741 have inclined, forwardly facing surfaces 742 
that join smoothly with the front wall 712 of the rear wall 710. 
Referring to FIGS. 8, 11 and 12, an enlarged head formation 755 is formed 
at the forward end of the post 720. The head formation 755 has front and 
rear surface portions 774, 775 that extend between outer and inner end 
surfaces 759, 760. While the outer end surface 759 aligns with and is 
effectively an extension of the outer end surface 729 of the post 720, the 
inner end surface 760 extends more closely toward the center axis 101 (as 
viewed in FIG. 11) than does the rounded inner end surface 727 of the post 
720. While the front surface portions 774 are relatively flat and extend 
substantially parallel to the front and rear surfaces 712, 714 of the rear 
wall 710, the rear surface portions 775 are inclined at a small angle 771 
(see FIG. 12) of only about five degrees relative to the generally 
parallel planes of the front surfaces 712, 774. 
The manner in which one of the cam bodies 600 is moved into and out of 
latching engagement with one of the keeper bodies 700 now will be 
discussed in conjunction with FIGS. 12-15. Referring to FIG. 12, when 
latching engagement is to be initiated, the lock rod 120 is caused to 
pivot the cam bodies 600 so that the long arms 620 are pointed into the 
space defined between the keeper posts 720, 740. Referring to FIG. 13, as 
the cam body 600 is rotated counterclockwise about the rearwardly moving 
pivot axis 101 to latchingly engage the keeper body 700, the inner end 
region 760 of the enlarged head formation 755 is received within the 
U-shaped recess 660 of the cam body 600. 
The extension rightwardly (as viewed in FIGS. 12-15) of the inner end 
region 760 of the keeper body 700 is of importance in defining the shape, 
location and operation of an "abutment surface" 775 of the keeper, as will 
be brought out shortly. What may be observed by comparing the depictions 
of FIGS. 12 and 13 is that, because the inner end region 760 extends 
rightly as far as it does, the presence of the U-shaped recess is rendered 
necessary for, without the recess 660 to receive and wrap about the 
rightwardly projecting end region 760, it would not be possible to move 
the cam body 600 toward and into latching engagement with the keeper body 
700. 
Referring to FIG. 14, as the cam body 600 continues to rotate 
counterclockwise about the pivot axis 101, the U-shaped recess 660 "wraps 
about" the inner end 760 of the head formation 755 to bring a rounded 
portion 690 of the cam body 600 (located at the juncture of the U-shaped 
recess 660 and the front surface 625 of the long arm 620) into engagement 
with the rear surface 775 of the head formation 755 to force the cam body 
600 to continue to move rearwardly (to force closed the door 60 to which 
the cam body 600 is connected by the lock rod 120). At the same time that 
engagement of the rounded portion 690 of the cam body 600 with the rear 
surface 775 is forcing the door 60 closed, the progressively greater 
engagement that is being caused to take place between the primary 
engagement surfaces 630, 730 (as the wedge-shaped post 720 is received to 
greater depths within the V-shaped notch 622) will cause relative axial 
movement (along the pivot axis 101) that will eliminate any misalignment 
that may be present of the center planes 601, 701 of the cam and keeper 
bodies 600, 700 so that any vertical misalignment that may exist between 
the cam and keeper bodies 600, 700 will thereby be corrected as the door 
60 is closed. 
As continued counterclockwise rotation of the cam body 600 about the pivot 
axis 101 takes place, a progressive increasing degree of "latching 
engagement" may be said to result that culminates when the cam body 600 is 
brought into what is referred to herein by such interchangeable terms as 
"a position of full latching engagement" or, more simply, "fully latched 
engagement" with the keeper body 700--it being understood that, as a 
position of full latching engagement is reached by the cam and keeper 
bodies 600, 700, the door 60 is concurrently brought to its "fully closed 
and latched position," also referred to herein as its "fully closed 
position." 
Referring to FIGS. 9 and 15 wherein a cam body 600 is shown in a position 
of full latching engagement with a keeper body 700, it will be seen 1) 
that the wedge-shaped cross-sections of the posts-720, 740 are fully 
received within the V-shaped notches 722, 744 so that the engagement of 
the primary engagement surfaces 630, 730 acting in concert with the 
engagement of the secondary engagement surfaces 650, 750 will function to 
strongly resist relative axial movement of the latchingly engaged cam and 
keeper bodies 600, 700 (whereby racking will be inhibited due to 
suppression of axial movements of the locking rod 120 relative to the door 
frame portions 30, 40); 2) that the rearwardly facing surface portions 646 
of the short arm 640 are in engagement with the forwardly facing surface 
portions 742 of the wedge-shaped corner formations 741; and, 3) that the 
forwardly-facing flat surface 625 of the long arm 620 is fully engaging 
the rearwardly-facing flat surface 775 of the enlarged head formation 755. 
The flat surfaces 625, 775 constitute "abutment surfaces" that engage when 
the cam and keeper bodies 600; 700 are fully latched. When engaged as 
depicted in FIG. 15, the abutment surfaces 625, 775 serve the important 
function of transmitting from the cams 130, 140 to the keepers 230, 240 
major portions of door loading forces that are imposed the door 60 by 
shifting or shifted loads or the like (i.e., forces that tend to open the 
door 60 in opposition to the latched engagement of the cam and keeper 
bodies 600, 700); and, it is due in large measure to the engagement of the 
abutment surfaces 625, 775 that the door 60 is prevented from opening when 
it is latched closed. 
Features of the present invention reside in the location, orientation and 
configuration of the abutment surfaces 625, 775--and in the fact that, 
when the door 60 is fully latched and closed, the abutment surfaces 625, 
775 engage "one flat surface against the other." 
The location of the abutment surfaces 625, 775 is quite close to the 
location of the pivot axis 101--which is due both to the fact that inner 
ends of the engaging surfaces 625, 775 extend rightwardly (as viewed in 
FIG. 15) toward the pivot axis 101, and to the very "compact" 
configurations of the cam and keeper bodies 600, 700 which, though 
elongate, tend to be shorter than are many proposed cam and keeper bodies 
that currently are in commercial use. Due to the advantageous location of 
the engaging abutment surfaces 625, 775, door loading forces that are 
transmitted between the engaged surfaces 625, 775 (by force components 
that extend normal to the plane of the engaged surfaces 625, 775) act 
through an unusually short moment arm in generating torque about the pivot 
axis--torque that is undesired and should be minimized because it tends to 
pivot the cams 130, 140 out of latching engagement with the keepers 230, 
240. If the engaged surfaces 625, 775 were stationed at a greater distance 
from the pivot axis 101, force loadings of the same magnitude transmitted 
normally between the surfaces 625, 775 would act through a greater moment 
arm and would therefore tend to generate undesirable "unlatching torque" 
of correspondingly greater magnitude. 
The orientation of the engaged abutment surfaces 625, 775 is in a plane 
that very nearly parallels the plane of the door 60 (i.e., the plane of 
engagement of the abutment surfaces 625, 775 is inclined relative to a 
plane in which the door frame portions 30, 40 and the closed door 60 
extend by an angle of only about five degrees; which angle is designated 
in FIG. 12 by the numeral 771) is such that, when forces transmitted 
between the latched cam and keeper bodies 600, 700 are divided into 
segments that extend normal and tangential relative to the plane of 
engagement of the surfaces 625, 775, the tangential force components are 
of sufficiently minimal magnitude to not cause any significant unlatching 
movement of the cam and keeper bodies 600, 700. 
The flat configuration of the abutment surfaces 625, 775 also is 
advantageous in that it does not confine force transmission to only 
limited areas of the abutment surfaces 625, 775, but rather tends to 
spread out force transmission across the full areas of engagement to 
minimize generation of force concentrations that tend to cause breakage of 
the cams 130, 140 and/or the keepers 230, 240. The use of the flat 
abutment surfaces 625, 775 differs from many prior proposals wherein 
engaging surfaces of differing radii of curvature often have been used, 
the effect of which is to relegate the transmission of forces between cams 
and keepers to relatively small surface areas where cam and keeper 
engagement actually takes place. 
Referring once again to FIG. 14, as clockwise pivotal movement of the cams 
130, 140 relative to the keepers 230, 240 takes place during "unlatching" 
of the cams 130, 140 and the keepers 230, 240, the rear surface 626 and 
the rounded end region 629 of the cam body 600 is brought into engagement 
with the front face 712 of the rear wall 710 of the keeper body 700 to 
force the axis 101 to move forwardly and out of the space located between 
the posts 720, 740--whereby a significant assist is provided in breaking 
open the door 60. As this "unlatching" rotation of the cams 130, 140 
continues, the rounded end region 629 moves rightwardly along the front 
face 712 of the rear wall 710, the length of the long arm 620 is extended 
against the front face 712, and the axis 101 is forced forwardly (as in 
FIG. 13) until the cam body 600 is no longer being restrained by the 
keeper body 700 (as in FIG. 15), hence door opening may continue. 
While a variety of "orientation terms" such as "upwardly," "downwardly," 
forwardly," "rearwardly," "leftwardly," "rightwardly," "inwardly," 
"outwardly" and the like are used in this document, these terms should not 
be interpreted as being limiting. The door control mechanism 100 can be 
used in a wide variety of attitudes other than the vertically extending 
orientation that has been described; and the described cam and keeper 
features and interactions can be implemented in wide variety of 
orientations and arrangements. 
Although the invention has been described in its preferred form with a 
certain degree of particularity, it is understood that the present 
disclosure of the preferred form has been made only by way of example, and 
that numerous changes in the details of construction and the combination 
and arrangement of parts may be resorted to without departing from the 
spirit and scope of the invention as hereinafter claimed. It is intended 
that the patent shall cover, by suitable expression in the appended 
claims, whatever features of patentable novelty exist in the invention 
disclosed.