Core Trays

Abstract

The invention relates to a plastic drill core tray of the type having a plurality of longitudinally extending channels disposed in a side by side relationship which are dished in cross-section to contain a drill core. The effective contained angle of the cross-section at the dished bottom of the channels is greater than 90.degree.. The plastic tray is reinforced with elongated metal reinforcing ribs having a U-shaped cross-section. The ribs are adhered to adjacent longitudinally extending marginal areas of adjacent channels to provide longitudinally extending reinforcing means, and the contained angle of the cross-section of the tray at the adjacent longitudinally extending areas is less than 90.degree..

Parent Case Text

FIELD OF INVENTION

This invention relates to the manufacture of plastic trays for storing drill cores and the like and is a continuation-in-part of application Ser. No. 42770, field June 21, 1970, and now abandoned.

Description

PRIOR ART

The drill core trays which are presently in use in the mineral exploration industry are generally made from wood and have a surface formed to provide a plurality of longitudinally extending channels to receive the core samples. To ensure that the wooden trays are sufficiently strong to support drill cores it is necessary to make them of a substantial thickness, with the result that they are rather heavy and difficult to ship from one exploration drill site to another. While it is well known to make trays from plastic material the conventional vacuum formed tray is quite unsuitable for use as a drill core storage tray. A plastic tray having the strength required to support and store drill cores would have to be made from a very thick plastic material in order to have sufficient strength. A tray made from a very thick plastic material would be very expensive and would offer little advantage over the wooden construction presently known.

SUMMARY

By constructing a tray from a sheet of plastic material and arranging the core receiving channels close to one another, it has been found that the contained angle between the marginal areas of adjacent channels provides an area which may be readily reinforced to provide the strong lightweight tray. The contained angle between the marginal areas of adjacent channels may be arranged to be less than 90.degree. such that it is possible to insert a lightweight metal reinforcing rib between the marginal edges of the channel to reinforce the tray. The reinforced tray is inexpensive to manufacture using a vacuum forming process and it is light in weight.

According to an embodiment of the present invention, a storage tray comprises a plastic bottom formed of a plurality of parallel longitudinally extending channels, each having a dished cross-section with a contained angle at the bottom of more than 90.degree.. Each channel merges with an adjacent channel at the longitudinal edge. Transverse reinforcing ribs are adhered and complementary with the bottom and located at longitudinally spaced intervals. The tray is also reinforced by elongated metal reinforcing ribs which have a U cross-section. The arms of the U section are adhered to adjacent longitudinally extending marginal areas of adjacent channels.

PREFERRED EMBODIMENT

The invention will be more clearly understood with reference to the following detailed specification read in conjunction with the drawings, wherein:

FIG. 1 is a pictorial view of a tray according to an embodiment of the present invention;

FIG. 2 is a cross-sectional view of a mould showing a first step in the forming process;

FIG. 3 is a sectional view similar to FIG. 2 showing a second stage in the forming process;

FIG. 4 is a pictorial view of a mould illustrating the manner in which the reinforcing ribs are located prior to its vacuum forming of the tray;

FIG. 5 is an enlarged portion of a cross-section taken along the line 5--5 in FIG. 4;

FIG. 6 is a cross-section taken through a longitudinal reinforcing rib; and

FIG. 7 is a bottom perspective view of an alternative construction.

The numeral 10 refers generally to a tray according to this invention. It is made from a rigid vinyl sheet of plastic 12 having a thickness of about 0.040 inches. The tray 10 is formed with a plurality of parallel longitudinally extending channels 14, each having a dished cross-section adapted to receive contents in use. Adjacent channels merge along longitudinal edges.

Reinforcing ribs 16 of U cross-section are adhered to adjacent longitudinally extending marginal areas of adjacent channels 14. Ribs 16 are of steel about 0.031 inches thick (22 gauge). Transverse reinforcing ribs 18 are formed to complement the underside of the tray 12.

The advantage of this structure is derived from the combination of a plastic channelled bottom and longitudinal and transverse steel reinforcing members, the longitudinal reinforcing members being at the marginal areas where adjacent channels meet. The contained angle at the point where adjacent channels meet is important because it affects the longitudinal stiffness of the adhered longitudinal reinforcing member for a given gauge. These reinforcing members must be light in weight to achieve the overall objective of an inexpensive portable yet strong tray. The effective contained angle A of the U-shaped cross-section of the ribs should not be greater than 90.degree.. The preferred range is 45.degree., plus or minus 10.degree.. If the angle is larger, the reinforcing member will lose much of its stiffness longitudinally of itself and its effectiveness is reduced as a reinforcing member. The effective contained angle B of the cross-section at the dished bottom of the channels is greater than 90.degree. as indicated in FIG. 5. It is important that the reinforcing ribs 16 be at the marginal areas where adjacent corrugations meet to achieve the objective of lightness and economy. If the objective was to provide construction strength at any cost, the reinforcement could effectively be made at the dished bottoms of the channels, but the contained angle of the dished section is much larger than it is where the marginal portions of adjacent channel walls merge and for a given strength, more steel would be necessary.

The tray is preferably made by a vacuum forming process on a mould 24 illustrated in FIG. 4 of the drawings. The mould 24 has a foraminous moulding surface that is complementary to the underside of the tray to be formed, and in use one first locates the transverse ribs 18 in the recesses provided in the mould as illustrated at the right-hand end of FIG. 4 of the drawing. Following this, the longitudinally extending ribs 16 are placed over the peaks of the mould and the peaks 19 of the ribs 18. It will be noted that the peaks 19 of the ribs 18 are recessed to accommodate the longitudinal ribs 16. The ribs 16 and 18 are precoated with an adhesive of a type, which when heat activated, will form a bond with the plastic sheet 12. The rigid vinyl sheet 12 is then clamped in a position overlying the mould in the position shown in FIG. 2 of the drawings. The vinyl sheet is then heated to render it formable and the air is withdrawn from the mould by way of the platen illustrated in FIGS. 2 and 3 of the drawings. By applying a vacuum, the heated sheet 12 is drawn into the mould to conform with the upper surface of the mould as the interior of the mould is evacuated of air. Activation of the adhesive may require preheating of the steel.

FIG. 5 of the drawings shows the cross-sectional structure of a reinforced portion of the tray, from which it will be seen that the dished configuration of the channels is not affected by the reinforcing ribs 16 or 18, the rib 18 being formed with a recessed portion 19 at the peaks thereof to accommodate the longitudinal rib 16.

As indicated in FIG. 6 of the drawings, the contained angle A of the U-shaped rib is preferably in the range of 45.degree., plus or minus 10.degree..

The tray illustrated in FIG. 1 of the drawings has a length of about 60 inches and a width of about 71/4 inches and it is particularly suitable for storing drill cores in the mineral exploration industry.

The materials specifications are by way of example only and it will be apparent that reinforcing members of different thickness and plastic sheets of different thickness and proportions are possible within the scope of the invention.

It has been found that the transverse reinforcing ribs 18 are not necessary on a tray having five longitudinally extending channels with a total width of about 9 inches and length of about 4 feet or less. It has also been found that with a tray in the order of 4 feet or less long it is not necessary that the elongated metal reinforcing ribs 16 should extend for the full length of each channel. The reinforcing ribs 16 can extend for less than the full length of their respective adjacent channels but any cross-section of the tray through the channels must include at least two of the metal reinforcing ribs. A practical arrangement for a 4 foot long tray has been illustrated in FIG. 7 which shows a tray from the underside from which the longitudinally extending reinforcing ribs 16 are visible. It will be noted that the elongated metal reinforcing ribs 16 do not extend for the full length of the adjacent channels that they reinforce. The outside ribs start from an end of the tray and discontinue. The end portions of the two inside ribs are co-extensive with the end portions of the outside ribs. It will be noted that any cross section of the tray will include at least two metal reinforcing ribs and that at least one end portion of each rib is co-extensive with an end portion only of its adjacent rib. It is conceivable that with more than five channels there would be more than two co-extensive ribs at the center locations in which case the foregoing limitation would not be true of the center reinforcing rib.

It should also be noted that for use under extreme climatic conditions such as lower than 40.degree. below zero it may be desirable to additionally rivet the reinforcing members to the plastic in order to avoid separation under shock conditions.

Claims

What I claim as my invention is:

1. A tray comprising a plastic bottom formed with a plurality of parallel longitudinally extending channels, each having a dished cross-section with side walls that make a contained angle at the bottom of more than 90.degree. and each merging with an adjacent channel at a longitudinal edge, and elongated metal reinforcing ribs each having a U cross-section, the arms of the U being adhered to adjacent longitudinally extending marginal areas of adjacent channels, the contained angle of the cross-section of said tray at said adjacent longitudinally extending areas being less than 90.degree., and transverse reinforcing ribs adhered to and complementary to the cross-sectional shape of the said bottom.

2. A tray comprising, a plastic bottom formed with a plurality of parallel longitudinally extending channels, each having a dished cross-section with side walls that make a contained angle at the bottom of more than 90.degree. and each merging with an adjacent channel at a longitudinal edge, and elongated metal reinforcing ribs each having a U cross-section, the arms of the U being adhered to adjacent longitudinally extending marginal areas of adjacent channels, the contained angle of the cross-section of said tray at said adjacent longitudinally extending areas being less than 90.degree., said contained angle of a cross-section of said tray at the longitudinally extending areas being 45.degree., plus or minus 10.degree., and transverse reinforcing ribs adhered to and complementary to the cross-sectional shape of said bottom.