WO2000071431A1

WO2000071431A1 - Components for modular pallets

Info

Publication number: WO2000071431A1
Application number: PCT/CA1999/000409
Authority: WO
Inventors: Abbey Nash
Original assignee: Palletronix Corporation
Priority date: 1999-05-19
Filing date: 1999-05-19
Publication date: 2000-11-30
Also published as: AU3696699A

Abstract

A plastic post (24) for a pallet (10) includes a female part (26) which receives a male part (28) along a central axis (70). The female part (26) has ratchet tracks equally spaced in a circle of first radius centered on the central axis (70) of the female part (26), and sets of screw thread segments equally spaced in a circle of a second, smaller radius centered on the central axis (70) of the female part (26). Each of the ratchet tracks spans an angle of magnitude Ø1; each of the sets of screw threads spans an angle of magnitude Ø2. The ratchet tracks and sets of screw thread segments alternate such that each set of screw thread segments is between an adjacent pair of ratchet tracks. The male part (28) has complementary sets of screw thread segments equally spaced in a circle of the second radius centered on a central axis (71) of the male part (28) and each spanning an angle of magnitude Ø3. The male part (28) has pawls equally spaced in a circle centered on a central axis (71) of the male part (28) and each spaced from an adjacent set of complementary screw thread segments by tan an angle marginally larger than Ø2. The angle magnitude Ø1 is arranged to be less than the sum of Ø2 and Ø3. The parts (26, 28) interlock only in a single unique insertion orientation, and can be separated only by rotating the parts (26, 28) back the insertion orientation. In one embodiment, the post is adapted for use with a planar blank that folds into a pallet structure.

Description

Description Components for Modular Pallets Technical Field

The invention relates to pallets for supporting articles during shipping or storage, and more particularly, to modular pallets. Background Art

Pallets have generally had upper and lower decks formed of wood slats nailed across horizontal wood spacers or posts. If damaged, such pallets often cannot be repaired in a cost-effective manner, and the wood is discarded as waste. Modular plastic pallets have been proposed to reduce reliance on wood, and also to permit replacement of defective components. Another advantage to modular construction is that pallets can be knocked-down, reducing space requirements for storage or transportation.

Modular pallets have been proposed in which an upper deck is formed with clearance holes and circular plastic posts are mounted in the holes. The posts might typically comprise an upper male part that extends through a clearance hole in the deck and screw fits into a female part below the deck. To enhance rigidity, a lower deck may be used, and each posts may include a lower male part that screw fit from below into the female part of the post, thereby securing the upper and lower decks. Use of screw thread joints permits continuous adjustment of the spacing between components to accommodate variations in deck thickness.

In some prior art modular pallets, components of the posts can rotate and loosen in response to shocks and vibrations arising duriπ:; handling and shipping. To resist relative rotation, the components can be molded with detents, such as ratchet and pawl assemblies, that permit the components to separate only when significant forces are applied, as during actual disassembly. The combination of screw threads and detents can complicate interlocking of the components. A worker can potentially mate the components in various angular orientations. Certain orientations can limit the degree to which the components can be tightened to grip a pallet deck. Depending on construction, the components may lock proximate to an unlocking orientation, potentially releasing with only minor additional displacement. Unless a worker is attentive to how the components are initially received in one another, the resulting pallet can potentially fail. Disclosure Of The Invention

In one aspect, the invention provides a post for mounting in an opening in a pallet deck, which comprises male and female parts that interlock only in particular relative angular orientations. The female part comprises a central axis along which the male part is received, and the male part comprising a central axis that aligns with the axis of the female part during interlocking. The parts comprise complementary locking means that permit threaded adjustment of component spacing and provide detent functions to secure the parts against inadvertent loosening.

The locking means of one part comprises ratchet tracks and first sets of screw thread segments. The ratchet tracks are equally spaced in a circular arrangement of first radius relative to the axis of the part, and each track spans a sector angle of magnitude 0\ . Each sets of screw thread segments comprises the same number of segments, vertically registered and parallel. The sets are equally spaced in a circular arrangement of a second radius relative to the axis of the part, and each sets spans a sector angle of magnitude 02- The ratchet tracks and sets of screw thread segments alternate, each set of screw thread segments located circumferentially between a different pair of the ratchet tracks.

The locking means of the other part include second sets of screw thread segments and pawls. Each second set of screw thread segments comprises the same number of segments, vertically registered and parallel, and each second set is configured to mesh horizontally with any one of the first sets. The second sets are equally spaced in a circular arrangement of the first radius relative to the axis of the other part, and each second set spans a sector angle of magnitude 0%. The pawls are equally spaced in a circular arrangement, and each pawl has a track-engaging element spaced circumferentially by an angle of about magnitude 02 from a different second sets of screw thread segments. Each track-engaging element is located substantially at the second radius relative to the axis of the other part

The first sets of screw thread segments, the second sets, the ratchet tracks, and the pawls are equal in number. The first and second radii are selected so that the second sets of screw thread segments are offset radially relative to the ratchet tracks avoiding interference between those locking structures during insertion of the male part into the female part and relative rotation of the parts after insertion. The magnitudes 0 , 0ι and 03 are selected so that the first and second sets of screw thread segments interfere vertically when the male part is inserted axially into the female part except at relative angular orientations that are equally spaced circumferentially and equivalent for purposes of locking the components together. In preferred form, the magnitude 0\ is at least three times 02, increasing the extent to which the parts can be rotated relative to one another on their meshed screw thread segments, and 0^ is less than the sum of 02 and 03, ensuring that the threads remain meshed through the full range of relative rotation of the parts and do not permit axial separation of the parts.

Other aspects of the invention will be apparent from a description below of preferred embodiments and will be more specifically defined in the appended claims. Brief Description of the Drawings

The invention will be better understood with reference to drawings in which: fig. 1 is a perspective view of a modular pallet formed from a planar plastic blank and several plastic posts; fig. 2 is a perspective view showing the blank partially unfolded; fig. 3 is a vertical cross-section centrally through one post and a tubular pallet structure in which the post is mounted; fig. 4 is an exploded perspective view of the post; fig. 5 is a diagrammatic representation of the locking structures associated with the post; fig. 6 is a side elevation of an assembled, modular plastic pallet; fig. 7 is an exploded oblique view of the pallet of fig. 6; fig. 8 is a fragment oblique view of a post associated with the pallet of fig. 6; fig. 9a shows the relative orientation of detent projection of the post and cooperating detent slots associated with a retaining track formed with lower deck of the pallet of fig. 6 when the post is insert by hand into the track; and, fig. 9b is similar to fig. 9a, but shows the relative orientation of the detent projections and slots after a significant axial compressive force has been applied momentarily to the post. Best Mode of Carrying Out the Invention

Reference is made to fig. 1 which illustrates a modular pallet 10. The pallet 10 includes a corrugated blank 12 which is initially planar but folds into an upper deck 14 and four tubular structures 16, 18, 20, 22 of generally rectangular cross-section that impart rigidity to the deck 14. The tubular structures 16, 18, 20, 22 are retained in their tubular orientation and reinforced with identical plastic posts, such as the post 24. The post 24 has a female part 26 that locates within the tubular structure 16 and serves as a rigid spacer, and upper and lower male parts 28, 30 (part 30 apparent only in figs. 3 and 4) that fasten to the female part 26 to secure the tubular structure 16 and deck 14.

Lateral flaps 32, 34, 36, 38 extend from each side of the deck 14 along hinge lines 40 pressed into the blank 12 during die-cutting. The flap 32 whose construction is typical comprises four rectangular panels 42, 44, 46, 48 joined by parallel hinge lines 50 that permit the flap 32 to be folded conveniently into the tubular structure 16. During such folding, one panel 42 locates uppermost and against a lower face of the deck 14 and another panel 46 locates lowermost and parallel to the lower face. Three posts are used to secure the tubular structure 16, including the post 24.

The mounting of the post 24 to the blank 12 is detailed in fig. 3. The post 24 mounts in a set of clearance holes: a large clearance hole 54 formed in the deck 14, a slightly larger clearance hole 56 formed in the upper panel 42, and a smaller clearance hole 58 formed in the lower panel 46. When the tubular structure 16 is assembled, the clearance holes 54, 56, 58 register vertically. The female part 26 of the post 24 is mounted within the tubular structure 16 between the upper and lower panels 42, 46. The upper male part 28 fastens to the female part 26 to secure the deck 14 and the upper panel 42. and the lower male part 30 fastens to the female part 26 to secure the lower panel 46. In more conventional pallets formed with separate upper and lower decks, the female part 26 would mount between the decks in alignment with clearance holes provided in the decks. For such purposes, the lower male part 30 and lower portions of the female part 26 may be made larger.

The pallet 10 is adapted to be lifted with a conventional forklift. In the tubular structure 16, two panels 44, 48 are oriented perpendicular to the lower face of the deck 14 when the tubular structure 16 is assembled. The panels 44, 48 are formed with clearance holes (shown in the partially unfolded blank 12 in fig. 2) dimensioned to receive the tines of a forklift. Two such clearance holes 66 register horizontally when the tubular structure 16 is formed to define a continuous horizontal passage through the tubular structure 16. Two other clearance holes 68 register during assembly of the tubular structure 16 to define another continuous horizontal passage spaced from the other passage according to the standard spacing associated with forklift tines. Similar clearance holes (not numbered) are formed in the opposing tubular structure 18 and define another pair of continuous horizontal passages that register horizontally with the passages of the tubular structure 16, allowing the forklift tines to extend fully through the two opposing tubular structures 16, 20. The other pair of opposing tubular structures 18, 22 are formed with similar clearance holes (not specifically indicated), thereby permitting a forklift to approach the pallet 10 from all four sides.

The general construction of the components of the post 24 will be described with reference to figs. 3 and 4. The female part 26 has a central axis 70 along which the upper male part 28 is received. The male part 28 has a central axis 71 (shown only in fig. 4) that aligns with the axis 70 of the female part 26 during interlocking. The male part 28 is molded with a circumferential flange 72 that butts against the upper face 74 of the deck 14 and a cylindrical side wall 76 centered on its axis 72. The female part 26 is molded with an annular shoulder 86 that locates the part 26 in the aligned clearance holes in the blank 12, an upper circumferential flange 88 that butts against the bottom of the upper panel 42, and an upper portion which defines a cylindrical side wall 90 dimensioned to receive the side wall 76 of the upper male part 28. When locked together, the parts 26, 28 grip the deck 14 and the uppermost panel 46 of the tubular structure 16 between their respective flanges 73, 88. The lower male part 30 has a circumferential flange 78 that butts against the lower panel 46 of the tubular structure 16, and a circumferential side wall 80 that inserts along the central axis 70 of the female part 26 into an internal lower cylindrical wall 82 formed in the female part 26 The lower male part 30 is substantially identical to the upper male part 28 but scaled to a smaller size.

The female part 26 and upper male part 28 have multiple sets of locking structures molded with their cylindrical side walls 76, 90 that mate when the upper male part 28 is inserted into the female part 26 in a particular relative angular orientation. The sets of complementary locking structures (screw thread segments, pawls, and ratchet tracks) are equal in number. In the description that follows, individual locking structures will be described with reference to the cross-sectional and perspective views of figs. 3 and 4. Complete sets of locking structures are shown diagrammatically and their reference numerals are found in fig. 5.

The locking structure of the upper male part 28 is molded externally on its cylindrical side wall 76. The locking structure includes four identical sets 92-98 (even numbers only) of screw threads segments in a circular arrangement centered on the axis 71. The set 92 apparent in fig. 3 and 4 is typical, comprising four identical screw thread segments, parallel and registered vertically. The locking structure of the upper male part 28 also includes four identical pawls 104-110 (even numbers only) in a circular arrangement centered on the axis 72. The pawl 104 illustrated in fig. 4 is typical, comprising a broad stem 112 defined by slots (not numbered) molded with the side wall 76 and a track-engaging element 114. The resilience of the stem 112 biases the track-engaging element 114 to a rest position shown in fig. 4, and permits elastic displacement of the track-engaging element 114 radially inward and outward relative to its rest position. In this embodiment, the pawls and sets of screw thread segments are substantially at a common axial position on the side wall 76; that is, these components are located substantially in the same general horizontal plane and consequently appear to be arranged in a single ring. The pawls 104-110 and the sets 92-98 of screw thread segments alternate, one set of screw thread segments being positioned between each adjacent pair of pawls and vice versa.

The complementary locking structure of the female part 26 is molded internally on its cylindrical side wall. The complementary locking structure includes four identical ratchet tracks 116-122 (even numbers only) equally spaced in a circular arrangement centered on the central axis 70. The ratchet track 116 shown in fig. 4 is typical, comprises a multiplicity of vertical teeth (not numbered)cooperating with the track-engaging elements of the pawls 104-110 in a conventional manner to constitute a detent. In this embodiment, the ratchet teeth are inclined in a clock-wise direction. Thus, when engaged by one of the track-engaging elements, each ratchet track resists relative rotation of the element in a counter-clockwise direction (as viewed from above) more strongly than relative rotation in a clock-wise direction. The complementary locking structure of the female part 26 also includes four sets 124—130 (even numbers only) of screw thread segments, also equally spaced in a circular arrangements. The set 124 apparent in fig. 4 is typical, comprising four screw thread segments, parallel and vertically registered. Each of the sets 124-130 is shaped and inclined to mate with any one of the sets 92-98 of screw thread segments molded with the upper male part 28. In this embodiment, the sets 124-130 of screw thread segments and ratchet tracks 116-122 are located at a common axial position within the female male part 26, and, alternate, with one set of screw thread segments between each adjacent pair of ratchet tracks and vice versa.

The relative orientation of the complementary locking structures of the female part 26 and the upper male part 28 is shown in the diagrammatic view of fig. 4. Each of the ratchet tracks 116-122 associated with the female part 26 spans a sector angle of magnitude 0\, marginally less than 70 degrees in this embodiment of the invention. Each of the sets 124—130 of screw thread segments associated with the female part 26 spans a sector angle of magnitude 02, marginally less than 20 degrees in this embodiment of the invention. Each of the complementary sets 92-98 of screw thread segments associated with the upper male part 28 spans a sector angle of magnitude 03, about 65 degrees in this embodiment of the invention.

Several matters regarding the relative positioning of the locking structures should be noted. First, the exemplary pawl 104 of the upper male part 28 is spaced from the exemplary set 92 of screw thread segments of the upper male part 28 by an angle marginally larger than 02- Each of the remaining pawls 94, 96, 98 is identically spaced relative to an adjacent set 94, 96 or 98 of screw thread segments, owing to the equal spacing of all locking structures. Thus, the upper male part 28 inserts into and releases from the female part in the relative angular orientation illustrated in fig. 5. When so inserted, each of the pawls 104-110 is positioned at the counter-clockwise end of one of the ratchet tracks 116-122. From the insertion orientation shown in fig. 5, the upper male part 28 can be manually rotated with a handle 102 fully through an angle of magnitude 0\ clockwise relative to the female part 25.

Second, the insertion orientation shown in fig. 5 is unique for purposes of interlocking the parts 26, 28. If the upper male part 28 is oriented several degrees to either side of the insertion orientation, the sets 92-98 of screw thread segments of the upper male part 28 interfere vertically with sets 124-130 of screw thread segments of the female part 26. The parts 26, 28 will also mate in three other relative angular orientations spaced by multiples of 90 degrees from the insertion orientation shown in fig. 5 . Because of the equal spacing of locking structures, the four angular orientations are functionally equivalent. Thus, the upper male part 28 will consistently rotate through a maximum angle of 0\ whenever the male part 28 in inserted into the female part 26, 28, which in turn sets the extent to which the parts 26, 28 are drawn together. To maximize the capacity to draw the parts 26, 28 tightly about a deck, the angle value 02 representing the circumferential extent of each of the sets 124-130 of screw thread segments associated with the female part 26 should be kept small relative to the angle value 0\ representing the circumferential extent of each of the ratchet tracks 116-122 associated with the female part 26. The angle value 0\ is preferably at least twice the angle value 02-

Third, the angle values of the locking structures are selected to constrain removal only from the original insertion orientation. In that regard, the angle values are selected such that 0\ is less than the sum of 02 and 03 With reference once again to the insertion orientation shown in fig. 5, it should be noted that this arrangement constrains the sets 92-98 of screw thread segments and corresponding sets 124-130 to remain meshed through the full range of rotation available to the upper male part 28, which, as mentioned above, is limited to the circumferential extent 0\ of the ratchet tracks 116-122. Thus, a worker cannot inadvertently rotate the male part 28 counterclockwise to an unlocking orientation or a position proximate to an unlocking orientation.

Lastly, the sets 92-98, 124-130 of screw thread segments are radially offset relative to the ratchet tracks 116-122 to avoid interference between the screw thread segments and the ratchet tracks 116-122 during rotation of the upper male part 28 relative to the female part 26. The sets 92-98, 124-130 of screw thread segments of both parts 26, 28 are oriented in circular arrangements with the same radius. The ratchet tracks 116-122 are orient in a circular arrangement with a larger radius, sufficient to ensure that the tips of the ratchet teeth associated with the female part 26 are positioned radially outward of the sets 92-98 of screw thread segments associated with the upper male part 28.

It should be noted that the locking structures can be interchanged between the male and female parts 26, 28. For example, the ratchet tracks 116-122 and short sets 124—130 of screw thread segments can be molded with the exterior of the male part 28, and the pawls 104—110 and complementary sets 92-98 of screw thread segments can be molded with the interior of the female part 26. The number of sets of locking structures (pawls, ratchet tracks, and screw thread segments) can be varied, but a very large number of sets tends to limit the extent to which the male part 28 rotates relative to the female part 26, and the angular orientation of the screw thread segments may have to be adjusted, within practical limits, to obtain effective clamping action.

Reference is made to figs. 6 and 7 which shows a generally rectangular, plastic pallet 140 of modular construction. The pallet 140 includes a rectangular upper deck 142, a rectangular lower deck 144, and four horizontally elongate posts 146-152 (even numbers only) located between the decks 142, 144. The posts 146-152 are oriented perpendicular to one side 154 of the pallet 140, which will be referred to as the "insertion side 154", and to the opposite side 156 of the pallet 140. Four upper tracks 158-164 (even numbers only) are molded with an inner face 166 of the upper deck 142, and four lower tracks 168-174, with an inner face 176 of the lower deck 144, to retain the posts 146-152. To enhance structural rigidity, reinforcing flanges extend circumferentially along the rectangular periphery of each of the decks 142, 144 and inward relative to the inner faces 166, 176 of the decks 142, 144. The reinforcing flanges are spaced apart along the insertion side 154 of the pallet 140, and a single continuous reinforcing flange 178 or 180 is molded with each deck 142 or 144 along the opposite side 156 of the pallet 140, for reasons explained below. It should be noted that the pallet 140 comprises two unique modular components: the decks 142, 144 are identical plastic moldings, as are the posts 146-152.

The post 150 is typical. Only the general configuration of the post 150 is apparent in figs. 6 and 7. Components of the post 150 are shown in detail and numbered in figs. 8, 9a and 9b. The post 150 has an upper horizontal flange 182 retained by the upper track 162, a lower horizontal flange 184 retained by the lower track 172, and a vertical web 186 extending between the flanges 182, 184. A pair of rectangular openings (not numbered but apparent in fig. 7) are formed in the web 186 for purposes of receiving the tines of a forklift perpendicular to the insertion side 154 of the pallet 140. The post 150 includes an upper pair of detent projections 188, 190, molded on laterally opposing sides of the upper flange 182 proximate to one end 192 of the post 150. The transverse cross-section of the flanges 182, 184 is otherwise uniform from the detent projections to the opposite end 194 of the post 150 for free sliding in the tracks 162, 172. An identical lower pair of detent projections 196, 198 are molded on laterally opposite sides of the lower flange 184 and vertically registered with the upper detent projections 188, 190 (the lower detent projection 196 being apparent only in figs. 9a-9b). The detent projection 198 is typical and detailed in figs. 8, 9a and 9b. The detent projection 198 is molded together with a stem 200 oriented parallel to the lengthwise axis of the post 150. This permits the detent projection 198 to deflect elastically between a rest position (shown in fig. 9b) in which the detent projection 198 protrudes laterally from the flange 184 and a retracted position (shown in fig. 9b) in which the detent projection 198 located entirely within a recess in the flange 184.

The upper and lower tracks 168-174 are identically configured, and the lower track 172 associated with the post 150 is typical. To facilitate molding, the track 198 is not continuous, but instead is defined by four similar pairs of retaining members aligned with laterally opposing sides of the track 198. The retaining members 202, 204, which are typical, are formed within the perimeter of a rectangular opening (not numbered but apparent in fig. 6) in the lower deck 144 in essentially mirror-image relationship. This configuration permits a mold part to be introduced through the opening 206 to define undercut surfaces of the retaining members 202, 204, significantly reducing the complexity of the required mold. The retaining member 204 comprises a vertical wall 208 extending inward from the inner face 176 of the lower deck 144, and a horizontal wall (not number but apparent in fig. 7) overlaying one side edge of the lower flange 184 and spaced relative to the inner face 176 of the lower deck 144 to secure the lower flange 184 against the inner face 176. The lower track 172 has an open end 212 at the insertion side 154 of the pallet 140 for receipt of the lower flange 184 of the associated post 150, and an obstructed end 214 at the opposite side 156 of the pallet 140. In this embodiment, the continuous reinforcing flanges 178, 180 molded with the upper and lower decks 142, 144 at the opposite side 156 of the pallet 140 serve as stops, obstructing the tracks 158-164 and 168-174. In each of the decks 142, 144, the reinforcing flanges are spaced along the insertion side 154 of the pallet 140 to define openings accessing the open ends of the tracks. The upper and lower access openings 216, 218 axially aligned with the upper and lower tracks 162, 172 are typical. The upper access opening 216 is defined by spacing an upper pair of reinforcing flanges 220; the lower access opening 218, by spacing a lower pair of reinforcing flanges 222. The access openings 216, 218 are vertically registered and positioned to permit the opposite end 194 of the post 150 to be inserted into the tracks 162, 172 until it engages the reinforcing flanges 178, 180 at the opposite side 156 of the pallet 140.

The upper and lower tracks 168-174, associated with the post 150 comprise identical pairs of detent slots, vertically registered, that cooperate with the upper and lower detent projections 188, 190, 196, 198 of the post 150 (lower detent projection 198 apparent only in figs. 9a-9b). Only the lower pair of detent slots 224, 226 appear in the drawings, specifically in figs. 9a-9b. The detent slots 224, 226 are formed in horizontal registration in the vertical walls of the pair of retaining members 202, 204 proximate to the insertion side 154 of the pallet 140. The relationship between the lower detent projection 198 and the lower detent slot 226 is typical. The detent projection 198 has a laterally outer surface 228 that tapers laterally inward toward the opposite end 194 of the post 150, and a surface 230 rearward of the tapered surface 228 that is oriented substantially perpendicular to the lower flange 184. When the detent projection 198 seats in the detent slot 226, the rearward surface 230 of the detent projection 198 seats against a surface 232 within the detent slot 226 oriented perpendicular to the axis of the track 172, to resist removal of the post 150.

The positions of the detent projections and the cooperating detent slots of the post 150 are carefully selected, as will be explained with reference primarily to figs. 9a-9b. In that regard, the detent projection 198 and cooperating detent slot 226 are typical. More specifically, the rearward surface 230 of the detent projection 198 is spaced a predetermined distance from the end 194 of the post 150, and consequently the same horizontal distance from the reinforcing flanges 178, 180 when the end 194 of the post 150 engages the flanges 178, 180. The seating surface 232 within the detent slot 226 is spaced a second distance from the reinforcing flange 180, corresponding to the predetermined distance less roughly one-sixteenth of an inch. In practice, a worker will insert the post 150 by hand into the associated upper and lower tracks 162, 172. When the majority of the lower flange 184 of the post 150 has been inserted into the lower track 172, the tapered surface 228 of the detent projection 198 eventually engages the retaining member 204 and deflects laterally inward. This allows further displacement of the lower flange 184 by hand relative to the track 172 until the post 150 engages the reinforcing flanges 178, 180. The detent projection 198 and slot 226 are then substantially in the relative orientation shown in fig. 9a. The other detent projections 188, 190, 196 are then similarly oriented relative to their respective detent slots.

Once the orientation of fig. 9a is achieved, the worker can no longer displace the post 150 by hand. The opposite side of the pallet 140 can be butted against a stationary surface, and the end 192 of the post 150 is then struck with tool, such as a hammer, applying a momentary, axial compressive force to the post 150. This causes the rearward surface 230 of the detent projection 198 to enter the detent slot 226 and engage the seating surface 232, as shown in fig. 9b, and causes the other detent projections 188, 190, 196 to locate in a similar manner in their respective detent slots. This arrangement ensures that the posts 146-152 are locked in consistent positions relative to the decks 142, 144, and tightly secured between the detent slots adjacent to the insertion side 154 of the pallet 140 and the reinforcing flanges 178, 180 at the opposite side 156 of the pallet 140. Eliminating play between the posts 146-152 and the decks 142, 144 renders the pallet 140 more stable and less likely prone to damage owing to shifting of components under heavy loads.

It will be appreciated that particular embodiments of pallets have been described and illustrated and that modifications may be made therein without necessarily departing from the scope of the appended claims.

Claims

1. A post for mounting in an opening in a pallet deck, the post comprising a male part for abutment against one face of the deck and a female part for abutment against an opposing face of the deck, the female part comprising a central axis along which the female part receives the male part, the male part comprising a central axis that substantially aligns with the central axis of the female part during such receipt of the male part, the parts comprising complementary locking means for interlocking the parts, characterized in that: the locking means of one of the parts comprises:

(a) ratchet tracks equally spaced in a circular arrangement of first radius relative to the axis of the one part, each of the tracks spanning an angle of magnitude 01;

(b) first sets of screw thread segments equally spaced in a circular arrangement of a second radius relative to the axis of the one part, each of the first sets spanning an angle of magnitude 02, each of the first sets located circumferentially between a different pair of the ratchet tracks, each of the first sets comprising the same number of screw thread segments vertically registered and parallel; the locking means of the other of the parts comprises:

(c) second sets of screw thread segments equally spaced in a circular arrangement of the first radius relative to the axis of the second part, each of the second sets spanning a sector angle of magnitude 03, each of the second sets comprising the same number of screw thread segments vertJaiJy registered and parallel, each of the second sets configured to mesh horizontally with any one of the first sets in different relative axial position;

(d) pawls equally spaced in a circular arrangement, each of the pawls comprising a track engaging element spaced circumferentially by an angle of about magnitude 02 from a different one of the second sets segments, each of the track engaging element located substantially at the second radius relative to the axis of the second part; the first and second radii are selected such that the second sets of screw thread segments are offset radially relative to the ratchet tracks during insertion receipt of the male part in the female part in a radial direction that avoids vertical interference between the second sets of screw thread segments and the ratchet tracks; the number of first sets, the number of second sets, the number of ratchet tracks, and the number of pawls are equal; and, the magnitudes 01, 02 and 03 are selected such that the screw first and second sets of screw thread segments interfere vertically when the male part is inserted axially into the female part except at relative angular orientations that are equally spaced circumferentially and equivalent.

2. The pallet post of claim 1 in which: the male part comprises a generally cylindrical side wall portion centered on the central axis of the male part and the female part comprises a generally cylindrical side wall portion centered on the central axis of the female part and dimensioned to receive the side wall portion of the male part; the ratchet tracks and the first sets of screw thread segments are molded at substantially a common axial position on the interior surface of the side wall portion of the female part, and the first sets of screw thread segments are offset radially inward relative to the ratchet tracks; and, the second sets of screw thread segments are molded at substantially a common axial position on the exterior of the side wall portion of the female part, and the track engaging element of each of the pawls is offset radially outward relative to the second sets of screw thread segments.

3. The post of claim 2 in which:

01 is at least three times 02; and, 01 is less than the sum of 02 and 03.

4. The post of claim 3 in which: the male part is an upper male part, and the side wall portion of the female part is an upper side wall portion; the post comprises a lower male part with a generally cylindrical side wall portion centered about a central axis of the lower male part, and the female part comprises a lower generally cylindrical side wall portion centered about the central axis of the female part and dimensioned to receive the side wall portion of the lower male part; the lower side wall portion of the female part is molded with sets of ratchet tracks and sets of second screw thread segments as required by claim 3 in respect of the upper side wall portion; and, the side wall portion of the lower male part is molded with pawls and sets of first screw thread segments as required by claim 3 in respect of the side wall portion of the upper male part.

5. The post of claim 4 in combination with a pallet structure formed from a unitary foldable planar blank, in which: the blank comprises a rectangular central portion with upper and lower faces and four sides, a lateral flap associated with each of the four sides and joined along a hinge line to the associated side, and a set of clearance holes associated with each of the lateral flaps and formed in the central portion proximate to the side associated with the lateral flap; each of the lateral flaps comprises a multiplicity of panels joined by parallel hinge lines about which the lateral flap is folded into a tubular structure with an upper one of the panels against the lower face of the central portion and a lower one of the panels parallel to and spaced from the lower face of the central portion, a set of upper clearance holes in the upper panel, and a set of lower clearance holes in the lower panel, each of the upper and lower clearance holes aligned with a different clearance hole of the set of clearance holes in the central portion associated with the lateral flap thereby forming sets of aligned clearance holes associated the tubular structure formed from the lateral flap; and, the female part of the post is seated within one of the tubular structures in alignment with one of the sets of the aligned clearance holes associated with the one tubular structure, the upper male part of the post is inserted into the one set of clearance holes from above and abuts the upper face of the central portion, and the lower male part of the post is inserted into the one sets of aligned clearance holes from below and abuts the lower one of the panels of the one tubular structure.

6. A generally rectangular plastic pallet comprising an upper rectangular deck with an inner face, a lower rectangular deck with an inner face, and a plurality of parallel, substantially identical posts located between the decks perpendicular to one side of the pallet and to an opposite side of the pallet, characterized in that: each of the posts is molded with an upper horizontal flange, a lower horizontal flange, an upper pair of detent projections on laterally opposing sides of the upper flange proximate to one end of the post and spaced a first predetermined distance from the opposite end of the post, and a lower pair of detent projections on laterally opposite sides of the lower flange and vertically registered with the upper pair of detent projections, each of the flanges having a substantially uniform transverse cross-section from the opposite end to the detent projections of the post comprising the flanges; each of the detent projections of each of the pairs of upper and lower detent projections is mounted on a molded stem such that the detent projection deflects elastically between a rest position in which the detent projection protrudes laterally from the flange with which the detent projection is molded and a retracted position in which the detent projection locates in a recess in the flange with which the detent projection is molded; each of the posts is associated with a pair of upper and lower tracks molded respectively with the inner face of the upper deck and the inner face of the lower deck, each of the upper tracks receives the upper flange of the associated post and is shaped to secure the received upper flange for sliding against the inner face of the upper deck along an axis perpendicular to the one side of the pallet, and each of the lower tracks receives the lower flange of the associated post and is shaped to secure the received lower flange for sliding against the inner face of the lower deck along an axis perpendicular to the one side of the pallet; each of the upper and lower tracks associated with each of the posts has an open end for sliding insertion of the associated post, an obstructed end limiting sliding of the associated post, and a pair of detent slots on laterally opposing sides of the track proximate to the one side of the deck and spaced a second predetermined distance from the obstructed end of the track, each of the pair of detent slots cooperating with one of the detent projections of the associated post; each of the detent projections of each of the posts has a laterally outer surface that tapers laterally inward toward the opposite end of the post such that the detent projection deflects laterally inward as the post is inserted into the associated tracks, and a surface rearward of the laterally outer surface substantially perpendicular to the flange with which the projection is molded; and, the first and second predetermined distances are selected such that each of the detent projections of each of the posts enters the cooperating detent slot only when the associated post engages the blind end of one of the associated tracks and a compressive force is momentarily applied to the one end of the associated post.

7. The modular pallet of claim 6 in which: each of the decks comprises reinforcing flanges extending circumferentially around the periphery of the deck and inward relative to the inner face of the deck; the reinforcing flanges of each of the decks are spaced apart at the one side of the pallet to define a plurality of access openings, each of the access openings of the upper deck is aligned with the open end of a different one of the upper tracks, each of the access openings of the lower deck is aligned with the open end of a different one of the lower tracks.

8. The modular pallet of claim 7 in which, in each of the decks, one or more of the reinforcing flanges at the opposite side of the pallet define the blind ends of the upper and lower tracks.