Self-contained latch constructions for interlocking containers in stacked relation

Each top cover of carrying and shipping containers designed for nested stacking has a first locking means for securing the cover to the container bottom. A second locking means for connecting each locked container to a similar underlying container positioned in stacked relation is located within the structure of a male component of the first locking means which is mounted in the container cover. Structures of both locking means are provided for rotary and linear sliding modes of operation. The second locking means include cam collars having upper and lower chambers, the latter housing followers which, when actuated by a finger manipulatable means accessible from the top of the containers, project and lock into the upper chambers of similar cam collars of underlying containers.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to finger manipulated latches for containers having 
separable fitted covers and being of the type used in shipping and storing 
reels of motion picture film and video or other magnetic tape cartridges 
and more particularly is directed to latch constructions having a dual 
capability, namely, of locking the cover to the container bottom and of 
connecting the locked container to a similar underlying container 
positioned in stacked nested relation. 
2. Description of the Prior Art 
Containers molded of high impact plastic having separable fitted covers are 
in popular use for storing, carrying and shipping, by mail or otherwise 
and without additional wrappings or packaging, reels of motion picture 
film and reels or cartridges of magnetic tape, such as videotape. Such 
container having self-contained interlocking means between the bottom and 
cover members and eliminating exterior binding straps or the like is 
disclosed in U.S. Pat. No. 3,297,153. 
The most popular and widely used shipping container of this type is sized 
to hold a single reel or cartridge. As an alternative to providing larger 
size containers for holding a plurality of reels or cartridges which 
comprise a single shipment or related subject matter, or packing a 
plurality of single unit containers in a larger shipping carton, or using 
cord, tape or straps to unite a plurality of single unit containers into a 
shipping unit, all of which constitute obvious disadvantages including 
significantly higher labor and material costs, there is a pressing need 
for a practical means for interconnecting two or more single unit 
containers to provide a unitary package to facilitate storing, carrying 
and shipping and which is preferably self-contained in a manner comparable 
to the latching means described in the above mentioned patent. 
SUMMARY OF THE INVENTION 
Among the objects of the invention is to satisfy the need hereinbefore 
stated by providing a locking unit having a "piggy-back" capability and 
comprising few and simple parts which may be manufactured by low cost 
quantity molding methods and which shall require minimum labor cost for 
assembly of the unit, per se, and for installing the unit in the fitted 
container cover. The locking unit shall also be capable, by simple finger 
manipulation, of interlocking its container with a similar container and 
locking unit in nested registration, one stacked upon the other, and which 
unit may include a latch for locking the cover to the container bottom in 
a commercially accepted and preferred fashion. 
The invention contemplates a locking unit comprising an outer tubular 
member or cam collar having upper and lower tracks formed as cam slots in 
the side walls thereof. An intermediate movable latch member or cam 
follower also of tubular configuration fits within te outer member and has 
upper pins engaging the lower tracks for controlled selective movement of 
the latch member between retracted and extended positions and lower pins 
adapted to releasably engage, as the latch member moves from retracted to 
extended position, the upper tracks of the outer member of a similar 
locking unit positioned in underlying stacked relation to effect 
interlocking therebetween. An inner member or actuator, accessible for 
finger manipulation from the upper end of the outer member, extends into 
the bore and engages the movable latch member to propel the latter between 
the retracted and extended positions as controlled by the engagement of 
the upper pins in the lower tracks of the outer tubular member in cam 
follower fashion. 
A feature of the preferred embodiment provides for a dual function 
capability by forming the outer tubular member with outwardly projecting 
latching elements and mounting the outer member for limited movement 
between open and locked positions in a separable fitted cover of a 
container for releasably engaging companion elements formed in the 
container bottom to lock the cover in closed position. 
Two alternate modes of operation, namely, rotary or linear sliding, may be 
utilized to achieve this dual function. For the rotary mode, the cam 
collar, cam follower and actuator, which comprise the locking unit, are 
generally of concentric cylindrical construction whereby rotary movement 
of the cylindrical outer member with respect to the cover and container 
bottom locks the cover in closed position and rotary movement, imparted by 
the actuator to the cylindrical intermediate movable member with respect 
to the outer member, will by the cam action therebetween interlock the 
stacked containers. Alternately, the cam collar, cam follower and actuator 
which comprise the locking unit for the linear sliding mode of operation 
are generally of rectangular cross-section and nested one within the other 
so that the rectangular outer member will slide with respect to the cover 
and container bottom for locking the cover in closed position and linear 
pressure applied to the innermost actuator imparts sliding movement to the 
intermediate movable member with respect to the outer member which, by the 
cam action therebetween, effects the interlocking of the stacked 
containers.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring in detail to the drawings, 20 denotes a shipping container, seen 
in FIGS. 1, 2, 3 and 4 to comprise a bottom 21 and a fitted cover 25 
formed to provide a chamber 20a for the contents thereof, such as, a 
videotape cartridge (not shown), between a pair of dual function rotary 
locking units 30, embodying the invention, and which impart the 
"piggy-back" interconnecting capability to container 20. 
For a clear understanding of the structure of rotary locking unit 30, 
reference is made to FIGS. 4, 6, 7, 8 and 9. Locking unit 30 comprises an 
outer tubular member 31, also referred to as a cam collar, an intermediate 
rotatable and extendable member 40, also referred to as a cam follower, 
and being of tubular configuration coaxially mounted within member 31, and 
an inner rotatable actuator 45 for propelling member 40 between retracted 
and extended positions. 
The outer tubular member 31 is generally cylindrical in shape but has an 
integral handle 32 extending laterally from one side of an upper end 
thereof. Handle 32 comprises a horizontal tapered plate 32a formed as a 
lateral extension of an intermediate external flange 34 spaced downwardly 
from a top flange 33, and a vertical medial rib 32b upstanding from plate 
32a to the level of top flange 33, the latter defining the upper finished 
edge of member 31. A retaining ring or shoulder 38 is integrally formed at 
a spaced distance below intermediate flange 34 and has a beveled surface 
for snap-in engagement and retention in a portion of cover 25 as 
hereinafter described. A pair of diametrically outwardly extending latch 
pins 31c, coplanar with rib 32b, are located adjacent the bottom edge of 
member 31 providing one element of the locking means between container 
cover 25 and bottom 21. An internal flange 39, substantially coplanar with 
intermediate external flange 34, provides a reduced bore central opening 
39a and is formed with a pair of diametric cutots 39b disposed at right 
angles to rib 32b. Internal flange 39 divides the bore of outer tubular 
member 31 into upper and lower chambers 31a and 31b. The cylindrical wall 
of outer tubular member 31 is formed with two pairs of diametric slots 35, 
36 arranged in vertical alignment and having similar configurations, 
namely, horizontal portions at the left ends of the slots merging with 
upwardly inclined portions at the right ends thereof. The upper pair of 
slots 35 are located in the wall of upper chamber 31a and have upper open 
ends 35a of the inclined portions formed as cutouts in top flange 33 and 
provide the female component of the latch for interlocking two nested 
containers 20 aided by protuberances 35b located on the horizontal 
portions of upper slots 35 adjacent the imclined portions thereof. The 
lower pair of slots 36 are closed ended and located in the wall of lower 
chamber 31b. A pair of fragmentary slots 37 extend upwardly from the 
bottom edge of member 31 and are in vertical alignment with the right 
closed ends of lower slots 36. 
Rotatable and extendable member 40 is sized to coaxially fit lower chamber 
31b with a slight projection beyond the bottom edge of member 31 when 
fully retracted, as shown in FIGS. 4 and 6, to facilitate stacking in 
nested alignment. As shown in FIGS. 4 and 9, two pairs of diametric pins 
43 and 44 extend radially outwardly from member 40 and are spaced in 
vertical alignment. Upper pins 43, having a cam follower function, are 
positioned adjacent the upper edges of member 40 and engage lower slots 
36. Lower pins 44 have a latching function with respect to upper slots 35 
of a similar locking unit 30 of an underlying nested container 20. As seen 
in FIG. 4, pins 44 are positioned inwardly of the lower edge of member 40 
a distance comparable to that which member 40 projects beyond member 31 
and fit into fragmentary slots 37 when in fully retracted position. A pair 
of diametric internal axially extending tracks 42a are provided between 
pairs of spaced internal ribs 42 located along a diameter at about 
45.degree. from the diameter of pins 43 and 44. To facilitate assembly and 
in cooperation with beveled surfaces 43a of upper pins 43 as hereinafter 
described, a diametric pair of axially extending slits 41, seen in FIG. 9, 
are located along a diameter at right angles to that of pins 43 and 44 and 
extend from open ends at the upper edge of member 40 to closed ends 
inwardly of the lower edge of member 40. 
Actuator 45 is here shown as a two-piece structure to provide a 
telescoping, extendable finger grip similar in both construction and 
method of manufacture to the telescoping rotary latch disclosed in 
copending patent application of Lazzaro A. Fattori, Ser. No. 705,520. As 
seen in FIGS 2, 6, 7 and 8, actuator 45 comprises an outer tubular body 46 
and an inner member 48 which telescopes into axial bore 46a except for a 
diametrically disposed and upstanding flange serving as finger grip 48a. 
Outer body 46 is diametrically sized to fit central opening 39a and 
terminates at the upper end adjacent finger grip 48a in a radially 
extending circular flange 47 sized to seat on internal flange 39 at the 
bottom of upper chamber 31a of outer member 31. A pair of diametrically 
opposed pointed projections 47a extend beyond the periphery of flange 47 
in right angular relation to finger grip 48a and selectively engage the 
snap-in indexing means formed as inclined projections 31d extending 
inwardly on the interior of the wall of upper chamber 31a. Retaining ring 
or shoulder 46d is spaced below flange 47 a distance substantially equal 
to the thickness of internal flange 39 and has a beveled surface for 
snap-in engagement and retention of actuator 45 in central opening 39a of 
outer member 31. The lower end portion of body 46 has a pair of 
diametrically aligned lateral lugs or pins 46e adapted to engage and ride 
along interior tracks 42a of member 40. Axial bore 46a, being of 
rectangular cross-section, has a lower portion which widens along one 
dimension forming opposite internal shoulders 46b against which exterior 
shoulders 49a of a pair of hook-like members 49 abut as a stop when inner 
member 48 is fully extended as shown in FIG. 7. Hook-like members 49 
terminate the lower end of inner member 48 and are provided with limited 
flexibility by diametric end groove 49b and a pair of side grooves 49c. 
The pair of opposite side walls of bore 46a which face hook-like members 
49 are formed with axially disposed, downwardly and inwardly tapered ribs 
46c which terminate short of the bottom end of tubular body 46 so that 
exterior shoulders 49a of hook-like members 49 clear the bottom ends 
thereof after hook-like members 49 are flexed toward each other by the 
taper of ribs 46c as inner member 48 is moved downwardly from the fully 
extended position shown in FIG. 7 to the fully retracted position shown in 
FIG. 6 and then freed for releasable retention by contact of exterior 
shoulders 49a against the bottom ends of ribs 46c. 
Container 20 is constructed to accommodate rotary locking units 30 at 
opposite ends thereof by having pairs of elongated wells 22 and 26 
depressed upwardly from bottom surface 21a and downwardly from top surface 
25a of container bottom 21 and cover 25, respectively. Wells 22 and 26 are 
located and sized to centralize each locking unit 30 on the longitudinal 
midline of container 20 with handles 32 extending in opposite directions 
in symmetrical fashion as seen in FIG. 1. The bottom walls 26a of wells 26 
have circular openings 26b formed with diametric cutouts 26c for passing 
pins 31c therethrough in permanently mounting locking units 30 in wells 
26. As seen in FIGS. 4 and 5, the depth of wells 26 are proportioned to 
align top flanges 33 with the top surface 25a of cover 25 when locking 
units 30 are mounted therein with horizontal plates 32a and intermediate 
flanges 34 resting on bottom walls 26a. Wells 22, being smaller along the 
short axis than wells 26, are sectionalized into lateral and medial 
portions by arcuate transverse sidewalls 22d. The medial portions of wells 
22 are proportioned to accommodate locking units 30 with laterally 
projecting pins 31c and have internal flanges 22a shaped to provide 
circular openings 22b and diametric cutouts 22c which are in registered 
alignment with openings 26b and cutouts 26c when cover 25 is in position 
on bottom 21. Flanges 22a are spaced inwardly from bottom surface 21a and, 
as seen from FIGS. 2 and 3, have radially extending ribs 22e formed on the 
bottom facing surfaces thereof along the counterclockwise edges of 
diametric cutouts 22c over which pins 31c of outer tubular members 31 snap 
to lock cover 25 to bottom 21 in the manner hereinafter described. 
The operation and utility of shipping containers 20 fitted with rotary 
locking units 30 will now be apparent. With cam collars 31 and cam 
followers 40, molded of a suitable plastic material, such as nylon, and 
two-piece actuators 45 molded and assembled as described in said Lazzaro 
A. Fattori patent application, each rotary locking unit 30 is assembled by 
first pressing the upper end of cam follower 40 into lower chamber 31b of 
cam collar 31. Slits 41 permit compression of cam follower 40 when beveled 
surfaces 43a of upper pins 43 engage the wall of lower chamber 31b 
enabling pins 43 to snap into lower slots 36. Cam follower 40 is rotated 
to the fully retracted position to align tracks 42a with cutouts 39b. 
Actuator 45 is inserted into upper chamber 31a with pins passing through 
cutouts 39b into tracks 42a and is then snapped into position by the 
coaction of the beveled surfaces of openings 39a and retaining ring 46d to 
permanently and rotatably seat on internal flange 39. Thus assembled, and 
with lateral latch pins 31c aligned with diametric cutouts 26c, a rotary 
locking unit 30 is snapped into position in each opening 26b in cover 25 
by coaction between the beveled surfaces of opening 26b and retaining ring 
38 to complete the assembly of cover 25. 
To position cover 25 on bottom 21, handles 32 of both locking units 30 are 
rotated to the counter-clockwise or open position, that is, with each 
handle 32 resting against the outer side of well 26, as shown at the right 
side of container 20 in FIG. 1. When handles 32 are so positioned, latch 
pins 31c align with cutouts 22c in container bottom 21 enabling the lower 
ends of cam collars 31 to pass through openings 22b to either replace or 
remove cover 25 from bottom 21. The arrangement of wells 22 and 26 with 
handles 32 of locking units 30 extending in opposite directions on 
opposite sides of container 20 allows cover 25 to be positioned on bottom 
21 in either possible 180.degree. orientation and eliminates the necessity 
of a particular orientation by cover 25 with respect to bottom 21. 
With cover 25 properly seated on container bottom 21 as hereinbefore 
described, the locking of container 20 is readily accomplished by applying 
pressure in a clockwise direction, as seen in FIG. 1, to medial ribs 32b 
of handles 32 to cause latch pins 31c, as will be clear from FIGS. 2 and 
3, to snap over ribs 22e into engagement with flanges 22a as handles 32 
move into abutment with the inner sides of wells 26. In this locked 
condition cam followers 40 are normally retained in the fully retracted 
position by projections 47a of flanges 47 engaging inclined projections 
31d as is clear from FIG. 8. 
When two locked containers 20 are in stacked relation, the bottom portions 
of cam followers 40 which project below cam collars 31 of the upper 
container 20 nest as alignment means in upper chambers 31a of lower 
container 20 and fragmentary slots 37 of the upper container 20 align with 
and terminate the open ends of upper slots 35 in the walls of upper 
chambers 31a of the lower container 20. To interconnect the two containers 
20 as a shipping unit, each finger grip 48a of the upper container 20 is 
rotated clockwise as seen in FIG. 1. Initially, sufficient force is 
exerted to snap projections 47a out of engagement with projections 31d 
freeing actuator 45 for continued movement whereby pins 46e engaging ribs 
42 impart the clockwise rotation to cam follower 40 while permitting 
relative axial movement therebetween. Each cam follower 40, controlled by 
upper pins 43 riding in lower slots 36, moves downwardly as it rotates so 
that the lower pins 44 thereof enter the inclined portions of uppe slots 
35 of the lower container 20, and after proceeding therealong, snap under 
protuberances 35b and into the closed horizontal left end portions of 
slots 35 to complete the attachment of the upper to the lower container 
20. In a similar manner, additional containers 20 may be stacked and 
attached one at a time to the top of an existing interlocked stack. 
To separate containers 20 from an interlocked stack, the uppermost 
container 20 is separated first by rotating each finger grip 48a in a 
counter-clockwise direction. An initial force is exerted to snap lower 
pins 44 under protuberances 35b and as lower pins 44 enter fragmentary 
slots 37 in the fully retracted position of cam follower 40, flange 
projections 47a will simultaneously snap over inclined projections 31d 
which prevent accidental extension of cam follower 40. In order to prevent 
the rotation of finger grip 48a from accidentally unlocking cover 25, the 
force required to snap lateral pins 31c over ribs 22e substantially 
exceeds the force required for snapping lower pins 44 under protuberances 
35b. The positioning of handle 32 and its vertical medial rib 32b, to 
which the force is applied in locking and unlocking cover 25, at a 
distance from the axis of rotation provides greater leverage than finger 
grip 48a to compensate for this additional force requirement. 
After separation from a stack, container 20 is readily opened by unlocking 
cover 25 by the application of pressure to medial ribs 32b to rotate 
locking unit 30 counterclockwise, as seen in FIG. 1, returning handles 32 
to their open positions against outer walls of wells 26. This serves to 
snap latch pins 31c from the position shown in FIG. 2 to that shown in 
FIG. 3, namely, over ribs 22e out of engagement with flanges 22a and into 
alignment with cutouts 22c, thus enabling cover 25 to be raised upwardly 
and removed from bottom 21. 
Since finger grip 48a is accessible, although awkwardly, for manipulation 
in its fully retracted position, it is understood that actuator 45 may be 
made in one piece. However, where the two-piece construction is provided 
as shown, prior to rotating actuator 45, an upward, pulling, force may be 
exerted on finger grip 48a to snap exterior shoulders 49a of hook-like 
members 49 over the ends of tapered ribs 46c releasing inner member 48 for 
axially sliding to the fully extended position shown in FIGS. 5 and 7 
wherein finger grip 48a projects above the top surface 25a of cover 25 for 
greater ease in manipulation. The coaction between hook-like members 49 
and tapered ribs 46c prevent inner member 48 from sliding downwardly into 
outer tubular body 46 until a deliberate downward force is applied to 
finger grip 48a to return the latter to the fully retracted position. 
Container 50, embodying the alternate mode of operation, is shown in FIGS. 
10 to 14, inclusive, to comprise container bottom 51 having fitted cover 
55 constructed to accommodate sliding locking units 60 at opposite ends 
thereof in pairs of elongated, aligned, through passageways 52 and 56 
formed, respectively, therein. Passageways 52, each having a rectangular 
cross-sectional area smaller than that of passageways 56, are each formed 
with opposite longitudinal sidewalls 53 and opposite transverse sidewalls 
54 extending upwardly from the bottom wall 51a of container bottom 51. 
Likewise, passageways 56 are each formed with opposite longitudinal 
sidewalls 57 and opposite transverse sidewalls 58 extending downwardly 
from the top wall 55a of cover 55. 
Locking unit 60 comprises an outer tubular member 61, also referred to as a 
cam collar, and being rectangular in cross-section, an intermediate 
slidable and extendable member 70, also referred to as a cam follower, and 
being of tubular configuration sized to slide within member 61 along the 
major axis thereof, and an inner actuator 75 for propelling member 70 
between retracted and extended positions. 
Outer tubular member 61 has an upper edge peripheral flange 63 and a pair 
of opposite intermediate exterior flanges 64 coplanar with an interior 
flange 69. One of the flanges 64 extends along each of the longitudinal 
walls 62 and flange 69 divides the hollow bore of member 61 into upper and 
lower chambers 61a and 61b. A pair of opposite exterior retaining 
shoulders 68 are formed at a spaced distance below flanges 64 and have 
beveled surfaces for snap-in engagement and retention of locking unit 60 
in passageway 56 of cover 55 as hereinafter described. A pair of outwardly 
extending latch pins 61c are centrally located adjacent the bottom edges 
of longitudinal walls 62 and provide one element of the locking means 
between container cover 55 and bottom 51. Two pairs of slots 65, 66 are 
formed in each longitudinal wall 62 and are arranged in vertical alignment 
and have similar configurations, namely, horizontal portions at the left 
ends of the slots merging with upwardly inclined portions at the right 
ends thereof, as observed in FIGS. 11, 12 and 13. The upper pairs of slots 
65 are located in the portion of walls 62 forming upper chamber 61a and 
have upper open ends 65a of the inclined portions formed as cutouts in top 
peripheral flange 63 and provide the female component of the latch for 
interlocking two stacked containers 50. The upper edges of slots 65 on the 
horizontal portions adjacent the inclined portions are formed with 
protuberances 65b. The lower pairs of slots 66 are closed ended and 
located in the portions of walls 62 forming lower chamber 61b. A pair of 
fragmentary slots 67 extend upwardly from the bottom edge of each 
longitudinal wall 62 and are invertical alignment with the right closed 
ends of lower slots 66. 
Slidable and extendable member 70 has a height to fit within lower chamber 
61b when fully retracted. The longitudinal sides 72 which face sides 62 of 
member 61 each has a pair of outwardly extending upper and lower pins 73 
and 74 arranged in vertical alignment so that one pin of each pair is 
located adjacent opposite ends of side 72 and are spaced vertically to 
register with the spacing of slots 65 and 66. Each upper pin 73 engages a 
lower slot 66 for cam follower function and each lower pin 74 has a 
latching function with respect to an upper slot 65 of a similar locking 
unit 60 of an undelying stacked container 50. As seen in FIG. 11, lower 
pins 74 fit into fragmentary slots 67 when member 70 is in fully retracted 
position. Transverse sides 71 are each formed with a medial cutout 71a 
extending from the upper edge of member 70 to short of the lower edge to 
facilitate assembly as hereinafter described. 
Inner actuator 75 is tubular and sized in cross-section to fit within 
member 70. Actuator 75 has an upper edge peripheral flange 77 which fits 
into the bottom of upper chamber 61a and rests on internal flange 69 of 
member 61. A pair of retaining shoulders 76 extend along longitudinal 
walls 75a which generally face the longitudinal walls 72 of member 70, and 
as seen in FIG. 14 are positioned above the upper edge of the latter when 
fully retracted. Retaining shoulders 76 are spaced below flange 77 to 
accommodate internal flange 69 therebetween. 
Longitudinal sidewalls 57 of each passageway 56 in cover 55 are formed with 
internal flanges 57a which are positioned to locate top peripheral flange 
63 in coplanar relation with top wall 55a when locking unit 60 is mounted 
in passageway 56 with intermediate exterior flanges 64 seated on flanges 
57a. Longitudinal sidewalls 53 of each passageway 52 are formed with 
inwardly extending latch bosses 53a serving as companion elements to latch 
pins 61c providing therewith the locking means between container cover 55 
and bottom 51. Downwardly facing and inclined surfaces 53b extend from the 
right ends of bosses 53a, as seen in FIGS. 11 and 12, and terminate at the 
left in semi-circular depressions 53c in which latch pins 61c seat in 
locked position. 
Linear sliding locking units 60 may each be assembled by pressing the upper 
end of member 70 into the bottom of lower chamber 61b of outer tubular 
member 61 so that the beveled surfaces of pins 73, engaging sidewalls 62 
and coacting with slits 71a, spring sidewalls 72 toward each other 
enabling pins 73 to snap into lower slots 66. Thereafter, inner actuator 
75 is inserted through upper chamber 61a into member 70 and, aided by the 
coaction between the beveled surfaces of internal flange 69 and retaining 
shoulders 76, is snapped into permanent position to slidingly seat on 
flange 69. Assembled locking unit 60 is inserted into passageway 65 and, 
by snapping the beveled surfaces of retaining shoulders 68 over the 
beveled edges of internal flanges 57a, is permanently and slidingly 
mounted on the latter. 
To provide a 180.degree. self-orientation feature for cover 55 with respect 
to bottom 51, comparable to that of container 20, it will be understood 
that locking unit 60 located on the left side of container 50 (not shown) 
will be arranged with associated parts, such as, latch bosses 53a on 
sidewalls 52, at 180.degree. with respect to those shown on the right side 
and illustrated in FIGS. 10 and 11. To close container 50, locking units 
60 are moved to open position, that is, for the unit 60 located on the 
right side of container 50, to the position shown in FIGS. 10 and 11, 
while for the unit 60 (not shown) located on the left side of container 
50, all positions hereinbefore and hereinafter described for locking unit 
60 will be in reverse. Thus in open position, latch pins 61c will clear 
latch bosses 53a permitting cover 55 to properly seat on bottom 51. 
To lock container 50, locking unit 60 is slidingly moved toward the left 
along passageway 56 from the position shown in FIG. 11 to that shown in 
FIG. 12 whereby latch pins 61c engage inclined surfaces 56b and snap into 
depressions 53c of latch bosses 53a. This movement of locking unit 60 is 
readily accomplished by finger pressure exerted on the left transverse 
wall of upper chamber 61a. 
Alignment means for stacking is provided by a pair of upstanding ridges 63a 
formed on opposite ends of peripheral flange 63, whereby ridges 63a of an 
underlying container 50 will project upwardly into passageway 52 and 
circumferentially engage portions of the bottom edge of cam collar 70 of 
the upper container 50. To interconnect two stacked containers 50, the 
finger is inserted through upper chamber 61a and into actuator 75 of the 
upper container 50 and pressure applied to move the actuator 75 to the 
left, as seen in FIG. 12, whereby cam follower 70, controlled by upper 
pins 73 riding in lower slots 66 of cam collar 61 moves downwardly while 
sliding toward the left causing the lower pins 74 thereof to enter the 
inclined portions of upper slots 65 of the lower container 50, and after 
proceeding therealong, to snap under protuberances 65b and into the closed 
horizontal left end portion of slots 65. The reverse procedures are 
followed to both separate containers 50 from the stack and to unlock and 
open cover 55. 
It is contemplated within the scope of the invention that stacking 
containers may be designed to utilize a single locking unit 30 or 60 
located centrally of the container, or more that the two locking units 
herein illustrated in containers 20 and 50. 
The shipping containers having locking units constructed for two alternate 
modes of operation, namely, rotary or linear sliding, and featuring the 
dual function capability of both locking the cover to the container bottom 
and interlocking an upper container to an underlying nested container as a 
shipping unit as herein disclosed are seen to achieve the several objects 
of the invention and to be well adapted to meet conditions of practical 
use. As various possible embodiments might be made in the above invention, 
and as various changes might be made in the disclosed constructions, it is 
to be understood that all matter herein set forth or shown in the 
accompanying drawings are to be interpreted as illustrative and not in a 
limiting sense.