US20070221102A1

US20070221102A1 - Vibration-isolating pallet and method of construction thereof

Info

Publication number: US20070221102A1
Application number: US11/389,291
Authority: US
Inventors: Per Reinhall
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-03-24
Filing date: 2006-03-24
Publication date: 2007-09-27
Also published as: CA2582625A1

Abstract

A vibration-isolating pallet and method of construction thereof are presented. A load bearing platform is oriented along a horizontal plane to form a substantially level upper surface that can be configured to receive a load. A base is oriented under the load bearing platform and along the horizontal plane to form a lower surface that can be configured to maintain a stationary position when placed on a level surface. A suspension system is fixedly interposed between the load bearing platform and the base. The suspension system is structured to allow relative motion between the load bearing platform and the base.

Description

FIELD OF THE INVENTION

The invention relates in general to pallets and, in particular, to a vibration-isolating pallet and method of construction thereof.

BACKGROUND OF THE INVENTION

Intermodal shipping is used throughout the industrialized world to efficiently and securely transport freight. Intermodal shipping involves the use of more than one mode of transportation, including rail, ocean carrier, aircraft, and trucks, without any handling of the freight when changing transportation modes. Thus, intermodal shipping provides faster freight transport, while reducing damage and shipping loss through improved cargo handling.
Pallets are widely used in intermodal shipping to provide flat transport structures to support goods while in transit in a stable and highly mobile fashion. Pallets are generally constructed of wood or other materials to provide a simple and low-cost structure that is generally considered disposable, although pallets constructed from plastics or high durability materials are intended for reuse. An ISO standardized pallet is approximately 40 inches wide by 48 inches deep by 5 inches high and is generally configured for two-way and four-way lifting using forklift-type devices. Other standardized and custom-sized pallets are also in use.
Increasing reliance on intermodal shipping has resulted in greater losses due to goods damaged in transit. A pallet must provide stability necessary to withstand severe shifting and the breakup of stacks during transit. Palletized loads, however, are susceptible to damage from loss of pallet stack unitization. Generally, a pallet is stacked with multiple layers of individual cartons or units of goods. Higher pallet stacks help reduce transportation costs through efficient pallet and space utilization. Fuel costs, time, and competitive forces compel manufacturers to maximize palletized loads for optimal space utilization, yet increased load sizes increases the potential for damage. Moreover, the costs of damaged and lost goods are now charged back to the manufacturer, who is faced with the problem of balancing the risks for expected losses against efficiencies gained through maximizing load out.
Vibration and the natural response frequencies of pallets are principal sources of damage to goods in transit, such as described in P.G. Reinhall and R. Carstens, “Achieving Effective Pallet Stack Unitization in Intermodal Shipping,” pp. 30-36, Packaging Tech. and Engr. (Apr. 1998), the disclosure of which is incorporated by reference. Freight is subjected to vibrations from the shipping means as an artifact of movement. Although shipping vibration forces are exerted three dimensionally, lateral vibrations are frequently more pronounced than longitudinal and vertical forces. Pallet natural frequencies are inherent to pallet structure, but resonance can vary based on the load height and weight. Overlaps of the resonance peak of a loaded pallet with peaks in the frequency spectra of shipping vibrations can cause potentially destructive resonance that can lead to loss of load integrity and subsequent damage to goods.
Currently, pallet stacks can be strengthened to increase resilience to compromise while in transit. For example, shrink wrap, liquid cohesives, and column stacking can be used to unitize and strengthen pallet stacks and to lessen the occurrence of pallet stack failure. However, these unitization techniques are costly in terms of time, expense, and convenience and must frequently be tailored for a particular load configuration.
Therefore, there is a need for a vibration-isolating pallet with a natural frequency substantially non-overlapping with transient variable shipping vibration peaks in power spectra. Preferably, such a pallet could be constructed at low cost, while be capable of anti-vibration tuning in one to three dimensions.

SUMMARY OF THE INVENTION

A pallet with tunable natural frequency properties and method for construction thereof are provided. The pallet includes one or more medial support members fixedly interposed as a tunable suspension system between a top load bearing layer and a bottom base layer. Each tunable medial support member is constructed from materials to form a composite component that exhibits orthotropic properties to allow relative motion between the top load bearing layer and the bottom base layer. The selection of materials in each medial support and arrangement of medial support members between the top and bottom layers facilitates tuning of the resonance peak of the pallet under load and, in particular, tuning of response to shipping vibrations occurring maximally at peaks in lateral power spectra due to the shipping means.
One embodiment provides a vibration-isolating pallet and method of construction thereof. A load bearing platform is oriented along a horizontal plane to form a substantially level upper surface that can be configured to receive a load. A base is oriented under the load bearing platform and along the horizontal plane to form a lower surface that can be configured to maintain a stationary position when placed on a level surface. A suspension system is fixedly interposed between the load bearing platform and the base. The suspension system is structured to allow relative motion between the load bearing platform and the base.
Still other embodiments of the invention will become readily apparent to those skilled in the art from the following detailed description, wherein are described embodiments of the invention by way of illustrating the best mode contemplated for carrying out the invention. As will be realized, the invention is capable of other and different embodiments and its several details are capable of modifications in various obvious respects, all without departing from the spirit and the scope of the invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing, by way of example, a prior art pallet laden with a stacked load.
FIG. 2 is an exploded perspective view showing the prior art pallet of FIG. 1.
FIG. 3 is a graph showing, by way of example, a frequency response curve for measured intermodal shipping vibration.
FIG. 4 is a graph showing, by way of example, a frequency response curve for a prior art pallet laden with a stacked load.
FIG. 5 is a perspective view showing a medial support member for use in the prior art pallet of FIG. 1.
FIG. 6 is a transverse cross-sectional view showing the medial support member of FIG. 5.
FIG. 7 is a perspective view showing a vibration-isolating pallet, in accordance with one embodiment.
FIG. 8 is an exploded perspective view showing the vibration-isolating pallet of FIG. 7.
FIG. 9 is a graph showing, by way of example, a frequency response curve for a vibration-isolating pallet laden with a stacked load.
FIG. 10 is a perspective view showing a medial support member for use in the vibration-isolating pallet of FIG. 7.
FIG. 11 is a transverse cross-sectional view showing the medial support member of FIG. 10 at rest.
FIG. 12 is a transverse cross-sectional view showing the medial support member of FIG. 10 under load.
FIG. 13 is a transverse cross-sectional view showing a medial support member with a single compressible layer, in accordance with a further embodiment.
FIGS. 14-15 are transverse cross-sectional views showing medial support members with rollable support layers, in accordance with further embodiments.
FIGS. 16-17 are side views respectively showing a pallet at rest and under lateral load that is constructed with the medial support member with rollable support layer of FIG. 15.
FIG. 18 is a transverse cross-sectional view showing a medial support member with a combination of compressible and incompressible layers, in accordance with a further embodiment.
FIGS. 19-20 are side views respectively showing a pallet at rest and under lateral load that is constructed with the medial support member with combination compressible layers of FIG. 18.
FIG. 21 is a top view showing an arrangement of medial support members for use in the vibration-isolating pallet of FIG. 7.
FIGS. 22-23 are top views respectively showing arrangements of medial support members for use in vibration-isolating pallets, in accordance with further embodiments.

DETAILED DESCRIPTION

Prior Art Pallet Construction
Pallets have become a ubiquitous element of intermodal shipping. FIG. 1 is a perspective view 10 showing, by way of example, a prior art pallet 11 laden with a stacked load 12. By way of example, the prior art pallet 11 is constructed of wood or other highly-available, low-cost materials to provide a stable and flat shipping platform. Individual cartons or units of goods 13 are stacked into one or more layers to form a load 12. The pallet 11 and stacked load 12 must together exhibit stability sufficient to withstand vibrational forces exerted during transit, as further described below with reference to FIGS. 3 and 4.
Although the dimensions of pallets are fairly standardized, the selection and arrangement of the individual components that together form a pallet can vary. FIG. 2 is an exploded perspective view 20 showing the prior art pallet 11 of FIG. 1. Generally, the pallet 11 includes a load bearing layer 21, medial support layer 23, and base layer 24. In addition, a medial cross-support layer 21 can be interposed between the load bearing and medial support layers. Other layers either in lieu of or in addition to the foregoing layers are possible.
More particularly, the load bearing layer 21 includes one or more wood or framing members 25 that form a flat upper surface upon which a stacked load 12 can be placed. The medial support layer 23 includes one or more medial support members 27 a-i that are fixed to the lower surface of the load bearing layer 21 or, if provided, medial cross-support layer 22. Preferably, the medial support members 27 a-i are arranged to facilitate the lifting of the pallet by a forklift-type device in two-way longitudinal or four-way longitudinal and lateral directions. Each medial support member 27 a-i preferably includes a single block of wood, which provides the spacing necessary to accommodate lifting, as further described below with reference to FIGS. 5 and 6. The base layer 24 includes one or more wood or framing members 28 a-c that are fixed to a lower surface of one or more of the medial cross members 27 a-i to increase structural rigidity and to preserve the bottom surfaces of the individual medial cross members 27 a-i. Finally, the optional medial cross-support layer 22 includes one or more wood or framing members 26 a-c that are fixed between the lower surface of the load bearing layer 21 and the upper surfaces of one or more of the medial support members 27 a-i to provide cross support to the pallet in, for instance, a longitudinal or lateral direction. Other components, materials, and arrangements of elements are possible.
Frequency Response Curves
Goods in transit are generally subjected to vibrations while in transit that are exerted in three dimensions. FIG. 3 is a graph 30 showing, by way of example, a frequency response curve 33 for measured intermodal shipping vibration. The x-axis 31 represents shipping vibration frequency measured in Hertz (Hz). The y-axis 32 represents energy measured as acceleration power spectral density (G²/Hz). The average lateral power spectrums of measured rail and truck portions of intermodal shipping vibrations are represented by the frequency response curve 33.
The energy of motion due to vibration is distributed primarily between 2.0 Hz and 6.0 Hz for rail transportation and between 15.0 Hz and 23.0 Hz for truck transportation. Excitation of the lowest lateral mode of a stacked load 12 generally occurs during rail transportation with a peak in frequency spectra 34 due to shipping vibration occurring at about 4.0 Hz.
Although significant peak accelerations due to intermodal shipping vibrations occur along all three dimensions, the lateral movement of a stacked load 12 sufficient to cause high box-to-box interface stress and slippage will most likely result in failure. The amplitude of peak accelerations only becomes large if an input vibration contains significant energy and frequencies to which the stacked load 12 is sensitive. An indirect measure of total energy of input vibration to a stacked load 12 is the root mean square (RMS) of wood pallet acceleration. Empirically, longitudinal vibration RMS is lower than the vibration RMS exhibited in vertical and transverse directions and lateral vibration RMS is comparable to vertical vibration RMS. Id.
The natural frequencies of a pallet 11 can affect the stability of a stacked load 12 to a significant degree. FIG. 4 is a graph 40 showing, by way of example, a frequency response curve 43 for a prior art pallet laden 11 with a stacked load 12. The x-axis 41 represents frequency measured in Hertz (Hz). The y-axis 42 represents transmissibility. The frequency response curve 43 reflects the natural frequencies of a stacked load 12, which can be influenced by parameters that include stack geometry, box or container stiffness, and stack weight. A resonant peak 44 occurs at about 4.0 Hz. Other parameters can influence natural pallet frequency.
Shipping vibrations become particularly destructive when a peak in power spectra overlaps with a resonant peak in frequency response for a stacked load 12. Overlaps can cause unacceptably high response levels in the stacked load 12, even when RMS is moderate. Empirically, vertical shipping vibrations exhibit the most energy in the frequency range of 10.0 Hz to 13.0 Hz, within which a loaded stack 12 exhibits a high natural frequency. A pallet 11 is most insensitive to vertical shipping vibrations. Thus, a destructive resonant situation is avoided. Lateral shipping vibrations, though, exhibit maximum energy distributed over a wider frequency range than vertical motion. A significant overlap of frequency resonance peaks for stacked loads 12 and the lowest frequency peaks in power spectra due to lateral shipping vibrations occurs in the 1.5 Hz to 3.75 Hz range. Consequently, lateral shipping vibrations impart significant motion to a stacked load 12 due to resonance phenomena that can potentially lead to lateral destruction of the stack. The frequencies corresponding to shipping vibration peaks are dependent on various parameters that include the mode of transportation, gross weight of the transporting vehicle, and the speed of travel. Other parameters are possible. Fine tuning the location of the natural frequency of a stacked load 12 to avoid shipping vibration peaks is difficult due to the variability of shipping vibration peaks.
Prior Art Medial Support Member
Structurally, the medial support members 27 a-i most strongly influence natural frequency response. FIG. 5 is a perspective view 50 showing a medial support member 27 a for use in the prior art pallet 11 of FIG. 1. Conventionally, each medial support member 27 a is typically constructed from a single block of wood or similar high density material. The lateral support member 27 a must have sufficient structural strength to bear a proportionate share of the overall load for which the pallet is maximally rated.
The primary consideration in determining the materials used to construct each medial support member 27 a and the arrangement of the medial support members 27 a-i within a pallet 11 are dictated by load bearing considerations and not with fine tuning natural frequency response. Generally, each medial support member 27 a is composed from isotropic materials that exhibit the same mechanical properties in all directions. FIG. 6 is a transverse cross-sectional view 60 showing the medial support member 27 a of FIG. 5. The height 62 of each medial support member 27 a is a function of overall pallet height, while the width 63 of each medial support member 27 a is selected to facilitate lifting of the pallet 11 with a forklift-type device. For two-way pallets, a width 63 is selected to allow longitudinal insertion of forklift tines, while the depth (not shown) can be co-extensive with the overall depth of the load bearing platform layer 21 (shown in FIG. 2). For four-way pallets, width 63 and depth are both selected to facilitate longitudinal insertion of forklift tines.
Each medial support member 27 a is rigid and relatively unyielding in lateral directions 65 in response to forces applied in the vertical directions 64, such as due to the loading of a stacked load 12. As a result, each medial support member 27 a efficiently transmits lateral shipping vibration energy onto the stacked load 12, thereby exposing the stacked load 12 to potentially destructive lateral resonance.
Vibration-Isolating Pallet Construction
A pallet and method for construction thereof can be provided with natural frequency properties adjustable through orthotropic medial support members that form a tunable suspension system. FIG. 7 is a perspective view 70 showing a vibration-isolating pallet 71, in accordance with one embodiment. By way of example, the majority of the pallet 71 is constructed of wood or other highly-available, low-cost materials to provide a stable and flat shipping platform. Individual cartons or units of goods 13 are stacked into one or more layers to form a load 72 and the combined natural frequencies of the pallet 11 and stacked load 72 can be tuned to resist peak frequencies in power spectra, as further described below with reference to FIG. 9.
The medial support members are tunable to facilitate tuning of the resonance peak of a pallet under load and, in particular, tuning of response to shipping vibrations occurring maximally at peaks in lateral power spectra due to the shipping means. FIG. 8 is an exploded perspective view 80 showing the vibration-isolating pallet 71 of FIG. 7. Generally, the pallet 71 includes a load bearing layer 81, medial support layer 83, and base layer 84. In addition, a medial cross-support layer 81 can be interposed between the load bearing and medial support layers. Other layers. either in lieu of or in addition to the foregoing layers are possible.
More particularly, the load bearing layer 81 includes one or more wood or framing members 85 that form a flat upper surface upon which a stacked load 72 can be placed. The medial support layer 83 includes one or more tunable medial support members 87 a-i that are fixed to the lower surface of the load bearing layer 81 or, if provided, medial cross-support layer 82. The medial support members 87 a-i form a suspension system that is structured to allow relative motion between the load bearing and base layers.
Preferably, the medial support members 87 a-i are arranged to facilitate the lifting of the pallet by a forklift-type device in two-way longitudinal or four-way longitudinal and lateral directions. Each medial support member 87 a-i is constructed as a composite of component materials, or as a unitary structure similar structural properties, as further described below with reference to FIG. 10 et seq. The base layer 84 includes one or more wood or framing members 88 a-c that are fixed to a lower surface of one or more of the medial cross members 87 a-i to increase structural rigidity and to preserve the bottom surfaces of the individual medial cross members 87 a-i. Finally, the optional medial cross-support layer 82 includes one or more wood or framing members 86 a-c that are fixed between the lower surface of the load bearing layer 81 and the upper surfaces of one or more of the medial support members 87 a-i to provide cross support to the pallet in, for instance, a longitudinal or lateral direction. Other components, materials, and arrangements of elements are possible.
Frequency Response Curve
The medial support members 87 a-i allow the resonance peaks of the stacked load 72 to be tunably shifted. FIG. 9 is a graph 90 showing, by way of example, a frequency response curve 93 for a vibration-isolating pallet 71 laden with a stacked load 72. The x-axis 91 represents frequency measured in Hertz (Hz). The y-axis 92 represents transmissibility. The frequency response curve 93 reflects the natural frequencies of a stacked load 12, which can be influenced by parameters that include stack geometry, box or container stiffness, and stack weight. Other parameters can influence natural pallet frequency.
The natural frequencies of the stacked load 72 have been shifted by tuning the tunable medial support members 87 a-i that constitute the suspension system. The suspension system is tuned such that vertical stiffness exceeds one or both of lateral and longitudinal stiffness. In addition, the suspension system can be further tuned such that lateral and longitudinal stiffness are substantially equal. By way of example, the resonance peak 95 has been shifted to occur around 8.0 Hz and thereby avoids overlapping the lowest frequency peak 94 in the power spectra of lateral shipping vibrations that occurs at about 4.0 Hz. The shifting of the pallet natural frequency allows improved resilience to potentially destructive resonance, which would otherwise occur due to overlap.
In one embodiment, the lateral, longitudinal, and lateral stiffness of the suspension system are tuned such that the lowest combined natural frequencies of the pallet 71 and load 72 are less than a lowest peak frequency in power spectrum of the shipping vibration. In a further embodiment, vertical, longitudinal, and lateral suspension system stiffness are tuned such that the combined natural frequencies of the pallet 71 and load 72 occurring at a frequency that is lower than 2.0 KHz do not coincide with peak frequencies in power spectrum of the shipping vibration. Other stiffness tunings are possible.
Vibration-Isolating Medial Support Member Construction
Each tunable medial support member 87 a is constructed as a composite of component materials, or as a unitary structure exhibiting similar structural properties. FIG. 10 is a perspective view 100 showing a medial support member 87 a for use in the vibration-isolating pallet 71 of FIG. 7. In one embodiment, each tunable medial support member 87 a is fashioned in a plurality of layers, although a single layer could also be employed, provided the appropriate orthotropic properties were exhibited, as further described below with reference to FIGS. 11 and 12. The materials used in each layer are selected by density, compressibility, and flexibility and are sized and arranged to shift the resonance peaks of the loaded stack 72. For example, a compressible middle layer 102 could be fixedly interposed between a relatively incompressible top layer 101 and bottom layer 103. The resulting tunable medial support member 87 a accommodates stack geometry, box, or container stiffness, and load weight, as well as other parameters that can influence pallet natural frequencies.
Each of the tunable medial support members 87 a-i is constructed from materials to form a composite component that exhibits orthotropic properties to allow or limit relative lateral, longitudinal, and vertical motion between the load bearing and base layers. FIG. 11 is a transverse cross-sectional view 100 showing the medial support member 87 a of FIG. 10 at rest. In one embodiment, each medial support member 87 a provides some combination of lateral, longitudinal, and vertical flexibility or stiffness. Each medial support member 87 a can be fabricated from a non-uniform buildup of a material, preferably using a material that is compressible and which is formed into at least one layer. Additionally, each medial support member 87 a can further be fabricated with at least one layer of rigid material. Thus, the middle layer 112 can be constructed from compressible materials, such as rubber, foam, silicon, and similar materials, or could be a contained volume that overall provides an orthotropic effect, such as a rubber or elastic bladder filled with an incompressible gas or fluid or a compliant solid. Further, the top and bottom layers 112, 113 can be constructed from rigid materials, such as wood, plastic, metal, plywood, and so forth. Other compressible and rigid materials are possible. A width 115 is selected to facilitate two-way or four-way loading with forklift-type devices, while the height 114 is selected to adjust the height of the pallet while under load to a predetermined and standardized height.
In one embodiment, the height 114 of each tunable medial support member 87 a changes with the application of a stacked load, which exerts vertical forces 116 against the upper and lower layers 111, 113 that generates a response to lateral forces 117 in the middle layer 112. FIG. 12 is a transverse cross-sectional view 120 showing the medial support member 87 a of FIG. 10 under load. The height 121 of the tunable medial support member 87 a has decreased proportionate to the vertical load forces 123 generated by the stacked load 72. The middle layer 112 responds by compressing to a decreased vertical height 121 and by deforming outwardly 124 with a lateral offset 122 proportionate to the load weight.
The amount of stiffness, flex, compression, and deformity can be tuned. The composite construction of rigid upper layer 111 and lower layer 112 and compressible middle layer 112 enable each of the medial support members 87 a-i to impart shifted natural frequencies to the pallet 71. In particular, lateral shipping vibration energy is resisted in part through the use of a compressible material for the medial support members 87 a-i and by providing an orthotropic composite medial support member in place of rigid medial support members.
Compression and deformity of the tunable medial support members 87 a-i occur when a compressible material is used in the middle layer 112. However, tunable medial support members that exhibit orthotropic properties can also be constructed using other materials or composite constructions. Several examples will now be discussed.
Single Compressible Layer
First, a single layer of compressible material could be used in the middle layer of each tunable medial support member. FIG. 13 is a transverse cross-sectional view 139 showing a medial support member 131 with a single compressible layer 133, in accordance with a further embodiment. Top layer 132 and bottom layer 134 are constructed from rigid materials. The middle layer 133 is constructed from a compressible material, such as wood or foam, that deforms sufficiently when stressed to alter the resonance peak of the pallet 71 under load.
Rollable Support Layer
Second, the tunable medial support members could be constructed without compressible materials. FIGS. 14-15 are transverse cross-sectional views 140, 150 showing medial support members 141, 151 with rollable support layers 143, 153 in accordance with further embodiments. Referring first to FIG. 14, flexible members 142, 144 are oriented vertically and placed on opposite sides of a rollable support member 143. The flexible members 142, 144 and rollable support member 143 need not be compressible. The flexible members 142, 144 must permit vertical flex and the rollable support member 143 is preferably solid. The rollable support member 143 is solid and has a generally ovaloid cross section to allow omnidirectional horizontal rotation when the pallet 71 under load experiences lateral or longitudinal motion.
Referring next to FIG. 15, flexible members 152, 154 are similarly oriented vertically and placed on opposite sides of a rollable support member 153. The flexible members 152, 154 and rollable support member 153 need not be compressible. The flexible members 152, 154 must permit vertical flex and the rollable support member 153 is preferably solid. The rollable support member 153 is hollow and has a generally circular cross section to allow unidirectional lateral rotation when the pallet 71 under load experiences shear. However, the rollable support member 153 resist vertical and longitudinal motion.
FIGS. 16-17 are side views 160, 165 respectively showing a pallet 161 at rest and under lateral load that is constructed with the medial support member with rollable support layer 151 of FIG. 15. Referring first to FIG. 16, the rollable support members 153 provide vertical support to the load bearing layer and the load. Referring next to FIG. 17, the rollable support members 153 prevent significant vertical motion 186 when the base layer of the pallet experiences shear. The load bearing layer stays horizontal and significantly fixed in vertical orientation. The rollable support members 153 respectively roll along the bottom and top surfaces of the load bearing and base layers. Accordingly, the flexible members 152, 154 and rollable support members 153 provide lateral flexibility 187 in response to shear and flexing of the rollable support members 153 accommodate vertical motion 186 sufficient to alter the resonance peak of the pallet 71 under load.
Combination Compressible Layer
Finally, the composite could be a “sandwich” of alternating compressible and incompressible materials. FIG. 18 is a transverse cross-sectional view 170 showing a medial support member 171 with a combination of compressible and incompressible layers 174 a-d, 175 a-c, in accordance with a further embodiment. Alternating compressible and incompressible layers 174 a-d, 175 a-c are placed between a top layer 172 and bottom layer 173. Each of the compressible layers 174 a-d can be constructed from the same or different types of materials, with varying densities, thicknesses, and sizes. Similarly, each of the incompressible layers 175 a-c can be constructed from the same or different types of materials, with varying densities, thicknesses, and sizes. In one embodiment, the compressible layers 174 a-d are bonded to the top layer 172, incompressible layers 174 a-c, and bottom layer 173. The compressible layers 174 a-d are made up of thin layers of rubber or silicon steel, plastic, or wood and the incompressible layers 175 a-c are made up of steel, plastic, or wood. Other materials are possible. The combined layers form a sandwiched structure.
FIGS. 19-20 are side views 180, 185 respectively showing a pallet 181 at rest and under lateral load that is constructed with the medial support member with a combination of compressible and incompressible layers 174 a-d, 175 a-c of FIG. 18. Referring first to FIG. 19, the sandwiched structure of the compressible and incompressible layers 174 a-d, 175 a-c provides vertical support to the load bearing layer and the load. Referring next to FIG. 20, the compressible and incompressible layers 174 a-d, 175 a-c prevent significant vertical motion 186 when the base layer of the pallet experiences shear. The load bearing layer stays horizontal and significantly fixed in vertical orientation. The compressible layers 174 a-d distort horizontally. Accordingly, the compressible and incompressible layers 174 a-d and top and bottom layers 172, 173 provide lateral flexibility 187 in response to shear and distortion of the compressible layers 174 a-d accommodate vertical motion 187 sufficient to alter the resonance peak of the pallet 71 under load.
The medial support members 131, 141, 151, 171 present the use of alternate composite components by way of illustration and are not meant to represent a comprehensive or limiting survey of possible materials or composite constructions. Other materials or composite constructions are possible.
Vibration-Isolating Medial Support Member Arrangement
The arrangement and placement of the tunable medial support members 87 a-i between the load bearing layer 81, or, if provided, medial cross-support layer 81, and the base layer 84 can also be tuned to shift the resonance peaks of the loaded stack 72. In addition, a FIG. 21 is a top view 190 showing an arrangement 191 of medial support members 82 a-i for use in the vibration-isolating pallet 71 of FIG. 7. By way of example, the medial support members 82 a-i are arranged to facilitate the lifting of the pallet by a forklift-type device in four-way longitudinal and lateral directions. The medial support members 82 a-i could also be arranged to facilitate the lifting of the pallet by a forklift-type device only in two-way longitudinal directions (not shown).
The tunable medial support members 87 a-i within the pallet 71 are arranged to provide stable support to the loaded stack 72 and to evenly distribute 191 load mass across the load bearing layer 81. However, fewer, or more, tunable medial support members could be used to alter load mass distribution or to lower overall pallet cost, which may be particularly desirable when a low weight loaded stack 72 is expected. FIGS. 22-23 are top views 195, 200 respectively showing arrangements 196, 201 of medial support members 198 a-d, 203 for use in vibration-isolating pallets, in accordance with further embodiments.
First, intermediate medial support members could be omitted. Referring to FIG. 22, tunable medial support members 198 a-d are provided only at the corners of the pallet 197. Alternatively, corner medial supports could be omitted. Referring next to FIG. 23, only a single tunable medial support member 203 is provided in the center of the pallet 202. The respective arrangements of the tunable medial support members 198 a-d, 203 allow the load mass to remain evenly distributed 196, 201, even though intermediate and corner tunable medial support members are not used.
The medial support members 82 a-i, 198 a-d, 203 present arrangements and placements by way of illustration and are not meant to represent a comprehensive or limiting survey of arrangements and placements. Other arrangements and placements are possible, including arrangements and placements of tunable medial support members and conventional solid medial support members, such as described above with reference to FIGS. 5 and 6.
While the invention has been particularly shown and described as referenced to the embodiments thereof, those skilled in the art will understand that the foregoing and other changes in form and detail may be made therein without departing from the spirit and scope of the invention.

Claims

1. A vibration-isolating pallet, comprising:

a load bearing platform to be oriented along a horizontal plane to form a substantially level upper surface that can be configured to receive a load;

a base to be oriented under the load bearing platform and along the horizontal plane to form a lower surface that can be configured to maintain a stationary position when placed on a level surface; and

a suspension system fixedly interposed between the load bearing platform and the base, wherein the suspension system is structured to allow relative motion between the load bearing platform and the base.

2. A vibration-isolating pallet according to claim 1, the suspension system further comprising:

one or more support members that provide at least one of lateral, longitudinal, and vertical flexibility, wherein the support members resist at least one of longitudinal and vertical motion in response to shear acting on the pallet.

3. A vibration-isolating pallet according to claim 2, wherein each support member is fabricated from a non-uniform buildup of at least one layer of compressible material.

4. A vibration-isolating pallet according to claim 3, wherein the compressible material is selected from the group comprising rubber, silicon, plastic polymer, and an incompressible liquid or gas contained within a malleable vehicle.

5. A vibration-isolating pallet according to claim 3, wherein each support member further comprises at least one layer of rigid material.

6. A vibration-isolating pallet according to claim 5, wherein the rigid material is selected from the group comprising wood, metal, ceramics, plastic, and composite solids.

7. A vibration-isolating pallet according to claim 1, wherein the suspension system is tuned such that vertical stiffness exceeds at least one of lateral and longitudinal stiffness.

8. A vibration-isolating pallet according to claim 1, wherein vertical, longitudinal, and lateral stiffness of the suspension system are tuned such that natural frequencies of the pallet with the load occurring at a frequency that is lower than 2.0 kHz do not coincide with peak frequencies in power spectrum of shipping vibration.

9. A vibration-isolating pallet according to claim 1, wherein lateral, longitudinal, and lateral stiffness of the suspension system are tuned such that lowest combined natural frequencies of the pallet with the load are less than a lowest peak frequency in power spectrum of shipping vibration.

10. A vibration-isolating pallet according to claim 1, the suspension system further comprising:

one or more support members, wherein each of the support members are selected from the group comprising a unitary support member that includes a compressible middle layer interposed between a pair of horizontally-oriented rigid layers, a rollable support member that includes a ovaloid or round rigid member interposed between a pair of vertically-oriented flexible layers, and a composite support member that includes a plurality of compressible middle layers interposed between horizontally-oriented rigid layers.

11. A method for constructing a vibration-isolating pallet, comprising:

orienting a load bearing platform along a horizontal plane to form a substantially level upper surface that can be configured to receive a load;

orienting a base under the load bearing platform and along the horizontal plane to form a lower surface that can be configured to maintain a stationary position when placed on a level surface; and

fixedly interposing a suspension system between the load bearing platform and the base, wherein the suspension system is structured to allow relative motion between the load bearing platform and the base.

12. A method according to claim 11, further comprising:

including one or more support members that provide at least one of lateral, longitudinal, and vertical flexibility, wherein the support members resist at least one of longitudinal and vertical motion in response to shear acting on the pallet.

13. A method according to claim 12, wherein each support member is fabricated from a non-uniform buildup of at least one layer of compressible material.

14. A method according to claim 13, wherein the compressible material is selected from the group comprising rubber, silicon, plastic polymer, and an incompressible liquid or gas contained within a malleable vehicle.

15. A method according to claim 12, wherein each support member further comprises at least one layer of rigid material.

16. A method according to claim 15, wherein the rigid material is selected from the group comprising wood, metal, ceramics, plastic, and composite solids.

17. A method according to claim 11, further comprising:

tuning the suspension system such that vertical stiffness exceeds at least one of lateral and longitudinal stiffness.

18. A method according to claim 11, further comprising:

tuning vertical, longitudinal, and lateral stiffness of the suspension system such that natural frequencies of the pallet with the load occurring at a frequency that is lower than 2.0 kHz do not coincide with peak frequencies in power spectrum of shipping vibration.

19. A method according to claim 11, further comprising:

tuning lateral, longitudinal, and lateral stiffness of the suspension system such that lowest combined natural frequencies of the pallet with the load are less than a lowest peak frequency in power spectrum of shipping vibration.

20. A method according to claim 11, further comprising:

including one or more support members, wherein each of the support members are selected from the group comprising a unitary support member that includes a compressible middle layer interposed between a pair of horizontally-oriented rigid layers, a rollable support member that includes a ovaloid or round rigid member interposed between a pair of vertically-oriented flexible layers, and a composite support member that includes a plurality of compressible middle layers interposed between horizontally-oriented rigid layers.

21. A vibration-isolating pallet constructed according to the method of claim 11.

22. A vibration-resistant pallet, comprising:

a load; and

pallet framing, comprising:

an upper surface to receive the load for mobile transit;

a base surface positioned below the load surface; and

one or more medial support members fixedly interposed between the upper and the base surfaces of the pallet framing,

wherein the medial support members are tuned to shift a natural frequency of tilt of the load to be non-coincidental to a frequency of rotation of a vehicle upon which the load and pallet framing are situated while the vehicle is in motion.