Stamping device for sheet-metal ammunition tray

A stamping apparatus is provided for producing an ammunition tray from metal sheet template with interleaving parallel cutouts in conjunction with a shop press. The apparatus includes upper and lower tray dies, upper and lower binders, and a pair of bolsters. Each die has opposite external and internal sides. The external side has a depression pocket. The internal side has a die impression to shape the template. Each binder has a cavity. The tray dies are disposed between the binders. The bolsters are disposed for engaging the shop press to apply compressive force. Each bolster correspondingly inserts through the cavity and into the depression pocket. The template is disposed between lower and upper internal sides of respective the dies. The shop press applies compression to the bolsters for stamping the template by the dies into the ammunition tray.

BACKGROUND

The invention relates generally to production of metal ammunition packing trays. In particular, the invention provides an apparatus to press sheet metal into a stackable sheet metal tray for stowing bullet cartridges in an ammunition box.

Ordnance ammunition is conventionally packaged within trays composed of high density polyethylene (HDPE). Conventional HDPE cradle packaging can ignite from weapons impact, which can cause delayed cook-off reactions of damaged or undamaged rounds in the stowage container. This constitutes a serious hazard to the warfighter.

SUMMARY

Conventional ammunition dunnage trays yield disadvantages addressed by various exemplary embodiments of the present invention. Instead a dunnage tray for holding ammunition cartridges within an ammunition box container with stowage volume has been developed and referenced in parent applications. In particular, exemplary embodiments provide an apparatus to stamp the dunnage tray for holding ammunition cartridges from metal sheet template with interleaving parallel cutouts in conjunction with a shop press. The apparatus includes upper and lower tray dies, upper and lower binders, and a pair of bolsters.

In exemplary embodiments, each die has opposite external and internal sides. The external side has a depression pocket. The internal side has a die impression to shape the template. Each binder has a cavity. The tray dies are disposed between the binders. The bolsters are disposed for engaging the shop press to apply compressive force. Each bolster correspondingly inserts through the cavity and into the depression pocket. The template is disposed between lower and upper internal sides of the respective dies. The shop press applies compression to the bolsters for stamping the template by the dies into the ammunition tray.

In other exemplary embodiments, front and rear insert flanges disposed adjacent to the upper binder to secure the template from lateral motion. Additionally, exemplary embodiments provide that each binder includes an opposing pair of lateral extensions, a pair of first compression resistors connect each upper extension on the upper binder to respective each lower extension on the lower binder, each binder includes six second compression resistors along an outer side facing opposite corresponding the die, and the first and second compression resistors engaging the bench press to receive the compressive force together with the bolsters

DETAILED DESCRIPTION

One of the objectives of the exemplary embodiments presented herein includes improvement of the Insensitive Munition and safety properties of ammunition packaging. The exemplary non-flammable dunnage tray mitigates this hazardous risk. The disclosure generally employs quantity units with the following abbreviations: length in inches (in), mass in pounds (lbm) and so forth.

Recent testing of 25 mm (millimeter) caliber high explosive armor piercing ordnance for Insensitive Munitions (IM) evaluation revealed susceptibility of conventional HDPE packing trays used for decades by the United States armed services to catching fire in particular IM impact scenarios. Delayed cook-off reactions of remaining cartridge rounds caused by these burning trays were observed as long as forty-two minutes after the impact that initiated the reaction. This cook-off scenario poses a serious threat to personnel safety, as the cans containing burning trays do not necessarily emit large volumes of smoke and so can appear safe to approach from a distance.

Replacement of the tray material with something nonflammable, less flammable, or containing less potential chemical energy that satisfies other packaging requirements (cost, weight, vibrational, etc.) could eliminate this hazard. In this case, packaged units of ammunition have already reached their logistical weight limit, so any solution must weigh the same as or less than the conventional HDPE packing material.

For the purposes of this disclosure, a specific ammo can, the CNU-405/E packaged with unlinked 25 mm ammunition, is under examination, but the technology has broad applicability across any ammunition or ordnance packaged in trays of this type. Artisans of ordinary skill will recognize that the dimensions and stowage of unlinked ammunition described herein are exemplary and not limiting to other ordnance sizes.

Several materials were investigated that could serve as a replacement to HDPE. These included novel fire resistant or fire retardant plastics such as bishydroxydeoxybenzoin (BHDB), thermoplastics with lower potential energy such as polypropylene, reconstituted fiber-based products such as bagasse, well-characterized fire resistant meta-aramids such as Nomex™, and fireproof minerals such as vermiculite. Each of these was ultimately discarded due to such issues as insufficient Manufacturing Readiness Level, noxious off-gassing from combustion, poor workability and capacity to hold a constant shape, volumetric and weight requirements, vibrational requirements and humidity requirements. Ultimately, aluminum was selected as the candidate material with which to proceed.

FIG.1shows an elevation cross-sectional view100of an exemplary stamping apparatus110for stamping sheet metal into an ammunition tray for 25 mm bullets. The apparatus110, shown in cross-section A-A, includes an upper die120, a lower die125, an upper binder130, a lower binder135and a weighting pair of bolsters140that insert into corresponding depression mating pockets145of the dies120and125.

The upper and lower binders130and135each share a half-dozen inner compression resistor assemblies150. Each inner assembly150includes a helical die spring152, a washer154, a pair of thin hexagonal nuts156at the extremities of both binders130and135. Further, a threaded setup stud158passes through each of the inner assemblies150. The washer154restrains vertical movement of the spring152, while the nuts156prevent dislodging the washer154.

The apparatus110further includes a quad set of outer compression resistor assemblies160. Each outer assembly160includes a helical die spring162, a washer164, a pair of thin hexagonal nuts166on a threaded setup stud168. The washer154restrains vertical movement of the spring152, while the nuts156prevent dislodging the washer154. The upper bolster140includes a vertical pair of top handles170. The binders130and135each have longitudinally flanking horizontal pairs of side handles180. A compass rose190provides orientation with X (longitudinal), Y (lateral) and Z (vertical) directions for the assembly and separate components. The Y direction points aft, while the Z direction points upward.

FIG.2shows an isometric assembly view200of the apparatus110with cross-section A-A parallel to the X-Z plane. Proximal front flanging insert210and distal rear flanging insert220attach to the upper binder130, which includes flanges230that extend longitudinally. Similarly, the lower binder135includes flanges235that extend longitudinally. The inserts210and220attach to the upper binder130by socket head cap screws240. The outer compression assemblies160connect the longitudinal flanges230and235together and are flanked by ejector pins250with flat tips260protruding from the binder130. The top handles170attach to the (upper) bolster140on pads270secured by screws275. The side handles180attach to the flanges230and235on pads280secured by screws285.

The exemplary pressing operation using the exemplary stamping device110uses a conventional shop press (not shown). This shop press can be manual, hydraulic, benchtop configuration. The shop press includes a frame with vertical posts joined by an overhead bridge on which a piston-driven ram is mounted. A bed rests below the bridge to support the device110while being pressed by the ram.

The dies120and125, binders130and135, bolsters140, and flanging inserts210and220are composed of grade-4340 steel. The helical springs152and162are composed of chrome silicon steel. The washers154and164are composed of zinc plated grade-8 steel. The hex nuts156and166are composed of zinc plated grade-5 steel. The studs158and168are composed of black oxide steel. The socket head cap screws240are composed of black oxide steel. The ejector pins250are composed of nitride coated H13 tool steel.

FIG.3shows an isometric view300of the upper binder130. To produce a tray for 25 mm ammunition, the dimensions are approximately: nineteen inches long with the flanges230included, nine-and-a-half inches wide and two inches high, weighing about twelve pounds (12 Ibm). The binder130has an upper planar face310having a vertically oriented rectangular cavity320with rounded corners325flanked by six planar through-holes330. The cavity320is about twelve inches long and four inches wide to receive the bolster140.

The flanges230include outward holes340and inward holes350. The binder130also has longitudinal sides360and lateral sides370from which the flanges230protrude. The longitudinal sides360each include a horizontal rectangular slot380. The six inner compression assemblies150pass through the planar holes330. The ejector pins250pass through the outward holes340. The four outer compression assemblies160pass through the inward holes350.

FIG.4shows an isometric view400of the lower binder135. For the exemplary tray, the dimensions are approximately: nineteen inches long with the flanges235included, nine-and-a-half inches wide and two inches high, weighing about twelve pounds (12 Ibm). The binder135has a lower planar face410having a vertically oriented rectangular cavity420with rounded corners425flanked by six planar through-holes430. The cavity420is about twelve inches long and four inches wide to receive the bolster140.

The flanges235include outer holes440and inner holes450. The binder135also has longitudinal sides460and lateral sides470from which the flanges235protrude. Each lateral side470includes a vertical extension480. The compression assemblies150pass through the planar holes430. The ejector pins250pass through the outer holes440. The compression assemblies160pass through the inner holes450.

FIG.5shows an isometric view500of the bolster140. For the exemplary tray, the dimensions are approximately twelve inches long, four inches wide and one-and-three-quarters inches thick, weighing about twenty-five pounds (25 lbm) each. The bolster140has an outer flat planar face510opposite a rounded inner planar face (hidden) that inserts into the pocket145of one of the dies120and125after passing through the cavity320of the upper binder130or the cavity420of the lower binder135.

The planar faces connect by longitudinal sides520and lateral sides530. A chamfered circular depression540about one inch in diameter is disposed in the center of the face510to serve as a centering feature for the ram of the shop press. Near the corners of the face510are a pair of holes550through which the screws275can be inserted for securing the upper handle170. Sides520and530join at rounded edges560.

FIG.6shows an isometric view600of the front flanging insert210. For the exemplary tray, the dimensions are approximately seventeen inches long and one-and-a-half inches tall. The insert210comprises a rectangular plate610and a lateral protrusion620that inserts into the slot380. A series of through holes630extend through the plate610and protrusion620for the socket head cap screws240to connect the insert210to the binder130. The plate610has an inner face640that abuts the binder130. The plate610and protrusion620share an upper face650. The plate610also includes a rounded edge660.

FIG.7shows an isometric view700of the rear flanging insert220. For the exemplary tray, the dimensions are approximately seventeen inches long and about three inches tall. The insert220comprises a rectangular plate710and a lateral protrusion720that inserts into the slot380. A series of through holes730extend through the plate710and protrusion720for the socket head cap screws240to connect the insert220to the binder130. The plate710includes a wall740that extends vertically downward. The plate710and protrusion720share an upper face750. The plate710and wall740have respective inner faces760and770that abut the binder130. The plate710also includes a rounded edge780.

FIGS.8A and8Bshow isometric views800of blank and cut metal sheets that the assembly110deforms to form an ammunition tray composed of aluminum 5052-H32.FIG.8Ashows a template sheet blank810with four rounded corners820. The blank810is about seventeen inches long and about ten inches wide with a stock thickness of 0.025 inch. Prior to stamping between the dies130and135, the blank810is subject to a punching operation to produce a tray template830.

FIG.8Bshows the template830with a fore row of seven cutouts840with corresponding base arcs845and an aft row of eight cutouts850with their base arcs855. The cutouts840and850each have a beer-bottle-silhouette arranged in parallel with the narrow neck portion oriented inward on the template830. (A beer-bottle silhouette constitutes a longitudinally joined pair of rectangular segments having distinguishable widths.) Lateral edge cutouts860are also shown to enable an operator's fingers to grasp the finished tray. A rear fold line870identifies the bending edge for the aft tab of the tray. A fore fold line880identifies the bending edge for the front tab of the tray.

FIG.9shows an isometric assembly view900of the upper die120. For the exemplary 25 mm ammo tray, the dimensions are approximately sixteen-and-a-half inches long, nine-and-a-third inches wide, and one-and-a-quarter inches tall. The die120includes an internal planar side910with an impression face that engages the template830, with longitudinal sides920and lateral sides930. The planar side910includes a fore row of seven rounded protrusions or rounded hills940and an aft row of eight rounded depressions or rounded valleys950interleaving each other in parallel with adjacent longitudinal separation of about one inch. The protrusions940and950correspond to and align with the respective cutouts870protrusions845and850.

The sides920and930join at rounded edges960. Each proximal and distal face for the longitudinal sides920of the upper die120includes a horizontal slot970. The lateral protrusion620of the rear flanging insert220engages the slot970of the proximal face (shown). The lateral protrusion720of the front flanging insert210engages the slot970of the distal face (hidden). These inner slots970align with corresponding outer slots380of the upper binder130. The bolster140inserts into the pocket145on an external side opposite the planar side910after passing through the cavity320of the upper binder130.

FIG.10shows an isometric assembly view1000of the lower die125. For the exemplary tray, the dimensions are approximately sixteen-and-a-half inches long and nine-and-a-third inches wide. The lower die125includes a planar face1010with an impression face that engages the template830, with longitudinal sides1020and lateral sides1030. The planar side1010includes a fore row of seven rounded depressions1040and an aft row of eight rounded protrusions1050. The depressions1040and protrusions1050interleave each other and correspond to the respective cutouts870and880to indent the template830. The sides1020and1030join at rounded edges1060. The bolster140inserts into the pocket145on an external side opposite the planar side1010after passing through the cavity420of the lower binder135.

FIG.11Ashows plan and elevation views1100of a completed ammunition tray1110that results from the dies120and125stamping against the template830via the apparatus110.FIG.11Bshow an isometric view1120of the tray1110. Along its longitudinal edges, the tray1110includes aft arc tabs1130and fore arc tabs1135respectively disposed along seven cradles1140that form an aft row1145, and eight cradles1150that form a fore row1155.

Folding the aft base arcs845and the fore base arcs855yields the respective tabs1130and1135. The cradles1140and1150constitute interleaving indented positions formed from respective cutouts840and850. An aft rib1170bends downward from the longitudinal edge along the rear fold line870, and a front rib1180also bends downward from the longitudinal edge along front fold line880in relation to the compass rose190. These ribs1170and1180serve to stiffen the tray1110.

Aft indentations1160inwardly extend from the cutouts840(extending from the necks of their bottle-silhouettes) to seat corresponding ogive tips of their respective ammo rounds. Similarly, fore indentations1165inwardly extend from the cutouts850. The arc tabs1130and indentations1160in the aft cradles1140can thereby seat seven ammo rounds. The arc tabs1135and indentations1165in the fore cradles1150can thereby seat eight ammo rounds. Edge lips1190further reinforce the cradles1140and1150to restrict lateral sliding of their seated ammo rounds.

FIGS.12A and12Bshow isometric views1200of ammunition trays1110to hold ammunition rounds1210.FIG.12Afeatures a single tray1110positioned up-side-down1220, whileFIG.12Bfeatures a pair1230of stacked trays1110with the upper unit above the up-side-down lower unit. This can be observed by orientation of the ribs1170and1180facing each other upward from the lower tray1110and downward from the upper tray1110.

A lower row1240of rounds1210points aft (e.g., towards the rear flanging insert220upon removal of the tray1110from the device110). An upper row1250of rounds1210points forward (e.g., similarly towards the front flanging insert210). The arc tabs1130and1135both block outward spilling from the bases1260of the rounds1210, while the indentations1160and1165inhibit motion from the ogive tips1270of these rounds1210.

The cradles1140and1150hold ammo rounds1210in position and inhibit migration from vertically adjacent trays. The bases1260of the rounds1210are disposed along the longitudinal edges of the tray1110adjacent the folds1170and1180, while ogive tips1270point inward. When stacked, these trays1110can be vertically inserted into a CNU-405/E ammunition can. An analogous tray developed for these purposes together with the ammo container are described in U.S. Pat. 10,845,174.

The exemplary tray stamping device110comprises two halves, an upper die assembly and a lower die assembly. The upper die assembly includes the upper die120, which is held in close contact against an upper binder130through the six inner compression assemblies150. The setup stud158of each of these inner compression assemblies150threads into the upper die120. The upper binder130is then disposed over these six studs158. A helical die spring152is disposed around each stud158and vertically secured by washer154and two hex nuts156on their corresponding studs158. To prevent movement or loosening during operation of the stamping dies120and125, the hex nuts156are preloaded against one another in a “jam nut” configuration.

The protrusions620and720of their respective flanging inserts210and220are then inserted into respective slots380of the upper binder130and then corresponding slots970of upper die120and secured in position with six socket head cap screws240per flanging insert. A lower die assembly comprises the lower die125, the lower binder135and six inner compression assemblies150combined in a similar fashion as the upper die assembly. The lower die assembly incorporates no flanging insert, as corresponding slots are absent. Side handles180adorn the protrusions230and235of the respective upper and lower binders130and135. These side handles180serve as assembly aids to enable manual gripping of the binders130and135.

The exemplary stamping device110is almost entirely steel, resulting in a total assembly weight of 213 lbm. The approximately 75 lbmfor the upper and lower die assemblies individually weigh about 75 lbm. As both bolsters140are steel, each one weighs approximately 25 lbm. When assembled together as a unit, the upper and lower die assemblies are oriented such that the upper die120and lower die125face opposite one another.

The upper and lower die assemblies interface with one another through a quad set of outer compression assemblies160with die springs162and a quad set of ejector pins250. The quad set of outer compression assemblies160is erected in a similar fashion as the previously detailed inner assemblies150. The purpose of the quad set of die springs162is to hold the dies120and125apart prior to a stamping operation for insertion of the template830and again after a stamping operation for removal of the finished tray1110.

The ejector pins250are precision ground stock items that enable precision alignment between the two dies120and125to prevent their interference or misalignment during stamping operation. The final parts of the stamping die device110are the bolsters140. A bolster140sits in a mating pocket145on the rear face of each upper die120and lower die125opposite their respective planar faces910and1010.

The bolsters140serve as interfaces between the bed and the ram of the shop press. These bolsters140act as stiff rigid structures that evenly distribute the concentrated loads from the press bed (or apron plate) and ram across the upper die120and lower die125to prevent their warping or distortion during the stamping operation.

Top handles170secure to the upper bolster140with screws275to aid in assembly of the device110. Additionally, the bolsters140do not physically attach to the upper and lower die assemblies. This reduces the combined weight that an operator has to move around during assembly. The assembly process for the exemplary stamping dies120and125includes disposing a bolster140on the bed of the shop press, then disposing the lower die assembly upon the lower bolster140. The upper die assembly can then attach to the lower die assembly via the quad packs of outer assemblies160and ejector pins250. An upper bolster140can then be disposed into the chamfered depression540atop the upper die120in the upper die assembly.

To produce a tray template830, a sheet blank810is prepared with appropriate cutouts840,850and860. To operate the exemplary stamping device, the template830is inserted between the two dies120and125, which rest on the edges of the lower binder135. The wall740of rear flanging insert220and interior walls480of lower binder135enable proper alignment of the template830in the device110.

The stamping operation then initiates with the ram of the bench press exerting force in the centering indentation540of the upper bolster140. This force compresses the quad set of weaker compression springs162, binding the template830between the outer edges of the upper and lower binders130and135.

As the bench press applies additional force, the quad set of outer die springs162can no longer compress, so the stiffer and stronger hex sets of inner die springs152begin to simultaneously compress. The load for the press transfers through the bolsters140to the upper and lower dies120and125, which advance simultaneously toward the restrained template830suspended between them.

As the upper die120advances toward the template830, so also do the front and rear flanging inserts210and220that affix to the upper die120via the slots970receiving their respective protrusions620and720. The dies120and125concurrently advance and stamp the template830from two opposing directions to form indentations1160and1165onto which ogive tips1270of the ammo rounds1210lay.

The dies120and125also bend the tabs1130and1135against which the bases1260of the ammo rounds1210rest against. Concurrently, the flanging inserts210and220bend the template830at a right angle downward (sandwiched by the lower die125) at the front and rear fold lines870and880to form respective stiffening tabs1170and1180on the template830.

Once the dies120and125have advanced fully, stamping of the tray1110is complete. Upon releasing the ram load from the bench press, the upper and lower hex sets of compression springs152unload, separating the two dies120and125from the tray1110and the quad set of springs162decompresses, separating the upper and lower die assemblies, thereby enabling the operator to remove the stamped ammunition tray1110, which is now ready for use.

This exemplary apparatus110provides both mechanism and technique to fabricate trays1110for improving munition/ordnance safety while deployed aboard ship and during transport and storage. The exemplary trays1110do not combust as do conventional HDPE trays, thereby improving safety. Being composed of sheet aluminum and utilizing folded edges, the configuration for the exemplary trays1110is stiffer, stronger and more reusable than the conventional tray arrangement as well at nearly the same mass. By comparison, the weights of the conventional and exemplary trays are 155 grams and 170 grams for 25 mm ammunition. Additionally, the stiffness reduces risk spilling of rounds1210compared to HDPE trays that bow substantially in the center when fully loaded with rounds1210.

An earlier prototype for a single bottle-shape mold was developed for proof-of-concept bench press stamping demonstration.FIGS.13A and13Brespectively show isometric and elevation exploded views1300of single round die components1310for testing. An upper block1320with a mount1325fastened thereto interfaces a lower block1330with a single round test die1335fastened thereto. A bottle-shape punch1340that attaches to the die1335can insert into a corresponding depression1345that extends through the lower die1335and the block1330.

FIGS.14A,14B and14Crespectively show isometric, elevation and cross-sectional elevation views1400of a single round test die assembly1410, developed as a prototype.FIG.14Aincludes cross-section positions A-A, B-B and C-C through the lateral Y-direction distributed along the longitudinal X-direction, while position D-D runs through the longitudinal X-direction along the center.FIG.14Cpresents Sections A-A1420, B-B1430, C-C1440and D-D1450, illustrating the screws1380,1385and1390through the blocks1320and1330.

FIG.15illustrates an isometric view1500of the upper block1320, which includes an inner face1510with corner holes1360and mount holes1520. The block1320is about eleven-and-seven-eighths inches long, six-and-a-half inches wide and one inch thick. The corner holes1360are about one-half inch in diameter and longitudinally spaced about ten-and-a-half inches apart. The mount holes1520are about a quarter inch in diameter.

FIG.16illustrates an isometric view1600of the mount1325with a recess face1610featuring block holes1620and punch holes1630within a rim1640. The mount1325is about ten-and-one-third inches long, five inches wide and a half inch thick. The block holes1620are chamfered and have diameters of about one-quarter inch to receive screws1380, while the punch holes1630have diameters of about one-quarter inch to receive screws1385.

FIG.17illustrates an isometric view1700of the punch1340, including a die face1710and mount holes1720. The punch1340is about seven-and-one-third inches long, one-and-one-quarter inches wide and a half inch thick. The mount holes1720align with the punch holes1730and are about one-quarter inch in diameter to receive screws1385.

FIG.18illustrates an isometric view1800of the lower block1330with a die face1810that includes a cavity1820and die holes1830. The block1330is about eleven-and-seven-eighths inches long, six-and-a-half inches wide and one inch thick. The corner holes1370are about a half inch in diameter and longitudinally spaced about ten-and-a-half inches apart. The cavity1820for receiving the punch1340is slightly more than seven-and-a-half inches long and a half inch deep. The die holes1830are about one-quarter inch in diameter to receive screws1390.

FIG.19illustrates an isometric view1900of the die1335including a receiving face1910with a punch slot1920and block holes1930. The die1335is about nine-and-three-quarters inches long, four-and-a-half inches wide and a half inch thick. The depression1345comprises the cavity1820and the slot1920to receive the punch1340. The block holes1930are about one-quarter inch in diameter and align with corresponding die holes1830to receive the screws1390.

The die1335fastens to the lower block1330by screws1390. The punch1340attaches to the mount1325by screws1385, which fastens to upper block1320by screws1380. An aluminum sheet (not shown but corresponding to the face1610) is disposed over the die1335. Then the blocks1320and1330are aligned to each other by the posts1350to form the test die assembly1410. The bench press stamps the assembly1410to shape the sheet into the bottle silhouette shape for containing a 25 mm round. Successful implementation of this design assembly1410facilitated development of the exemplary device110.