WO2022225389A1

WO2022225389A1 - A natural tree pole connector

Info

Publication number: WO2022225389A1
Application number: PCT/MY2022/050026
Authority: WO
Inventors: Dr. Wan Tarmeze WAN ARIFFIN; Dr. Khairul AWANG; Nik Adlin NIK MOHAMED SUKRI
Original assignee: Forest Research Institute Malaysia (Frim)
Priority date: 2021-04-20
Filing date: 2022-04-19
Publication date: 2022-10-27

Abstract

A natural tree pole connector comprising a casing (10) and a movable track (20) and a static track (30) within the casing. Each of the movable and static tracks comprise a V-shaped track and are disposed diametrically opposite each other such that the movable and static tracks define a diamond-shaped receptacle (40) for longitudinally receiving a portion of a natural tree pole. The movable track is movable to clamp the portion of the natural tree pole received within the receptacle, against the static track.

Description

A NATURAL TREE POLE CONNECTOR

This invention relates to a connector for structural constructs. More particularly, this invention relates to a connector for connecting natural tree poles in structural constructs.

DESCRIPTION OF THE PRIOR ART

Natural tree poles have been used for structural constructs throughout history and they have proven to be environmentally friendly, economical and reliable, surviving both the ravages of time and nature. Examples of natural tree poles typically used for structural constructs range from hardwood (e.g. oak, Eucalyptus grandis ), softwood (e.g. cedar, fir, pine) to woody grass (e.g. bamboo).

One major drawback of natural tree poles are the inherent geometric, mechanical and physical variabilities of individual poles, which reduce their reliability as a structural element. The geometric parameters (e.g. diameter, thickness, area, moment of inertia) of a natural tree pole can vary greatly along its length and these values can differ considerably from average values obtained by the idealisation of natural tree poles as straight circular tubes. The inherent geometric variation of the poles has a significant effect on their structural behavior and creates problems when developing an effective and practical joinery system for such poles.

WO 2016/049478 A1 discloses a connector for connecting bamboo poles. This prior connector comprises a connector segment (flexible tubular casing) for receiving bamboo poles and a hoop compression clamp positioned around the segment to secure the bamboo poles within the segments.

US 2014/0186096 A1 discloses a connector assembly for connecting natural tree poles comprising pivotally joined connector elements having a receiver tube and a collar. The collar is secured to the pole end in the receiver tube by means of bolts and screws and tightening the circular band positioned around the collar clamps the pole end in place. In both the prior connectors of WO 2016/049478 A1 and US 2014/0186096 Al, the natural tree poles are locked or clamped within the connectors by tightening a circular clamp or band around the circumference of the poles. Due to the diametrical variance of natural tree poles and the configuration of these prior connectors, such circular clamping of the pole inevitably results in imbalanced circumferential stress or hoop stress acting on the pole and this will lead to cracking of the pole (see Figure 4B).

WO 2012/034543 Al discloses a structural connector for connecting bamboo poles that comprises two concave plates placed in diametrically opposing positions on the outer surface of a pole. Each plate includes a bolt that is screwed into the pole, the bolt having a spring for accommodating diametrical variance of the pole. The plates are directly clamped onto the pole when the bolts are tightened.

EP 2 492 517 Al discloses a connection assembly for bamboo poles, which comprises a tensioning element (sheet metal strip) biased to exert radial compressive force on the bamboo pole, a pair of reinforcing concave plates placed at diametrically opposing positions on the outer surface of the pole and a bolt received through a transverse bore hole in the pole. The bolt is attached at each end to one of the reinforcing plates.

CN 202117176 U and CN 202023258 U disclose a connecting joint for connecting bamboo poles comprising tubular casings which are interconnected with each other by connecting nodes. A bamboo pole end is tightened to the connectors with stirrups, a steel hoop, a concrete core, embedded bars and reinforcing ribs. The steel hoop is sleeved onto the outer circumference of a bamboo pole end and the stirrups are wrapped onto the outer circumference of the steel hoop.

All of the prior connectors of WO 2012/034543 Al, EP 2 492 517 Al and CN 202117176 U and CN 202023258 U involve penetration of the natural tree poles (bamboo poles) with fastening elements (bolts). Such penetration of the natural tree poles results in concentrated loading stress at the bolt-points, which will lead to cracking of the poles over time. Additionally, use of such connectors that require penetration of the poles mean that any attempt to loosen or disassemble the connection for maintenance of the structural construction is very likely to lead to either structural weakening or structural failure of the pole at the bolt-points. Misalignment of the bolts in such connectors can also lead to imbalanced hoop stress on the pole.

Hence, there exists a need for the development of a natural tree pole connector that can accommodate the diametrical variance inherent in natural tree poles and enable secure connection of a natural tree pole without compromising its structural integrity.

This invention thus aims to alleviate some or all of the problems of the prior art.

SUMMARY OF THE INVENTION

In accordance with an aspect of the invention, there is provided a natural tree pole connector. The connector comprises a casing, a movable track and a static track within the casing. Each of the movable and static tracks comprise a V-shaped track and are disposed diametrically opposite each other such that the movable and static tracks define a diamond-shaped receptacle for longitudinally receiving a portion of a natural tree pole. The movable track is movable to clamp the portion of the natural tree pole received within the receptacle, against the static track. The shape and configuration of the movable and static tracks are such that the collinear points of contact between the movable track and the natural tree pole are diagonally opposing to those between the static track and the natural tree pole, resulting in a 45° inward radial force acting on the natural tree pole from each side of the receptacle.

In an embodiment, the casing may comprise a top portion, two side portions and a base portion. The casing may be rectangular in shape.

According to another embodiment, the movable track may comprise a top portion, a pair of spaced apart side portions and a base portion, with the top and side portions being planar and the base portion being an inverted V. In a further embodiment, the static track may comprise a pair of wedges, each wedge affixed to an opposing side of the casing base portion so as to define a V- shaped track therebetween.

According to an embodiment, the static track may comprise the base of the casing.

In yet another embodiment, the connector may further comprise a clamping mechanism for effecting movement of the movable track and locking in position the portion of the natural tree pole received within the receptacle.

The clamping mechanism may comprise an actuator anchored on the casing and operatively connected to the movable track. The actuator may be located at a point of longitudinal and lateral stability on the casing top portion such that the movable track can be maintained generally level, during movement.

The clamping mechanism may comprise a bolt receivable through a threaded hole on the casing top portion, the bolt operatively connected to a nut on the movable track top portion, wherein tightening or loosening the bolt effects movement of the movable track.

According to a further embodiment, the connector may be sized to receive natural tree poles having a diametrical variance of up to 2.0:1 (maximum to minimum ratio).

The connector may be sized to receive natural tree poles having a diametrical variance of 1.5:1 (maximum to minimum ratio).

The connector may be sized to receive natural tree poles having a diametrical variance of 1.25:1 (maximum to minimum ratio).

In an embodiment, the casing, the movable track and the static track may be made of the same material. The casing, the movable track and the static track may be made of wood, plastic or metal. In another embodiment, the casing, the movable track and the static track may be made of different materials. The movable track and/or the static track may be molded from a metal sheet.

In a second aspect of the invention, there is provided a combination joint comprising multiple units of the connectors. The joint may further comprise a modular joint adaptor. The joint may be a one-dimensional, a two-dimensional or a three- dimensional joint.

The present invention seeks to overcome the problems of the prior art by providing a natural tree pole connector that can accommodate the diametrical variance inherent in natural tree poles and enable secure connection of a natural tree pole without compromising its structural integrity.

The shape and configuration of the movable and static tracks within the casing (V- shaped track, movable track, static track) enables the connector of this invention to accommodate natural tree poles with varying diameters.

Further, disposing the V-shaped movable and static tracks diametrically opposite each other to define a diamond-shaped receptacle for receiving the natural tree pole enables the collinear points of contact between the movable track and the natural tree pole to be diagonally opposing to those between the static track and the natural tree pole. This results in a 45° inward radial force acting on the natural tree pole from each side of the receptacle and ensures an even distribution of load stress when the movable track is moved toward the static track, to clamp the pole against the static track. Such a uniform distribution of force also results in a balanced hoop stress about the circumference of the natural tree pole.

Additionally, no part of the connector of this invention penetrates into the portion of the natural tree pole held within the device. The connector can in fact be easily loosened or disassembled for maintenance of the structural construction without any effect on the structural integrity of the natural tree pole. The configuration of the connector is also relatively simple and straightforward. No specialized tools or skills are required to operate it and it is easy to use for assembly of a structural construction with natural tree poles.

Various other advantages of the connector of this invention will be further elaborated in the following pages.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated, although not limited, by the following description of embodiments made with reference to the accompanying drawings in which:

Figure 1 illustrates the casing, movable track, static track and clamping mechanism of a connector according to an embodiment of this invention.

Figures 2A and 2B show the static track fixed within the casing of the connector of Figure 1.

Figures 3A and 3B show the connector of Figure 1 with a portion of a bamboo pole clamped within the receptacle.

Figure 4A illustrates the 45° inward radial force acting on the natural tree pole (of Figures 3A and 3B) from each side of the receptacle.

Figure 4B (prior art) illustrates the imbalanced hoop stress resulting from the prior connector of WO 2016/049478 Al.

Figures 5A, 5B, 5C and 5D show four different dimensional configurations of a connector of Figure 1 when accommodating diametrical variance (maximum to minimum) of 1:1 versus 1.5:1; as well as 1:1 versus 1.25:1.

Figures 6A and 6B are schematic diagrams of a connector of Figure 1 showing an exemplary calculation of diametrical variance. Figures 7A and 7B are schematic diagrams showing the dimensions of exemplary connectors for accommodating bamboos within the 70 to 78 mm and 90 to 100 mm diameter ranges.

Figures 8A, 8B and 8C are schematic diagrams of a movable track of the connector of Figure 1 in a "sharp" configuration, a "plateau" configuration and a variant of the "sharp" configuration, respectively.

Figures 8D and 8E are schematic diagrams showing an exemplary calculation of diametrical variance of two embodiments of the movable track of Figure 8C.

Figures 9A and 9B illustrate calculation of the dimensions of the casing, movable track and static track relative to the maximum diameter of the natural tree pole to be accommodated.

Figure 10A shows the solid movable track of the connector of Figure 1.

Figure 10B shows a hollow movable track of another embodiment of the connector of Figure 1.

Figures 11A and 11B show two different dimensional configurations of an embodiment of the connector where the base portion of the casing defines the static track.

Figures 12A and 12B each show a singular unit of the connector of Figure 1 used to form an upright column and an inclined column, respectively.

Figure 13 shows a singular unit of the connector of Figure 1 when used in a raised configuration.

Figures 14A, 14B, 14C and 14D show four configurations of a combination joint comprising multiple units of the connector of Figure 1. Figure 15 show a circular modular joint adaptor used to enable formation of a combination joint of multiple connector units to form a roof apex.

Figures 16A, 16B and 16C each show combination joints where each connector unit is directly fixed together, separately bolted onto a base plate or both.

Figure 17 shows several combination joints used to form a temporary structural frame. Figure 18 shows connectors of this invention bolted to concrete stumps to form a car porch.

Figures 19A and 19B show the connectors of Figure 1 used to form an L-shaped brace and a T-shaped brace, respectively.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present invention relates to a natural tree pole connector. As seen in Figure 1, the connector mainly comprises a casing 10 and a movable track 20 and a static track 30 within the casing 10.

The casing 10 of the connector is generally an elongated housing that comprises a top portion 11, two spaced apart side portions 12 and a base portion 13. In an embodiment (e.g. Figure 1), the casing has a quadrilateral cross-section such as a square or a rectangle, and the top, side and base portions of the casing are planar. Alternatively, the casing could also be five sided with the top and side portions 11, 12 of the casing being planar and the base portion 13 comprising two inclined faces that taper to a point i.e. a V-shape, that defines the static track 30 (e.g. Figures 8 and 10).

The movable track 20 and static track 30 of the connector are configured within the casing 10. Both the movable and static tracks 20, 30 have elongated configurations with lengths that preferably match the depth of the casing 10. Both movable and static tracks 20, 30 are V-shaped and are disposed diametrically opposite each other within the casing 10 such that a diamond-shaped receptacle 40 is defined between the tracks 20, 30 for longitudinally receiving a portion of a natural tree pole (e.g. Figures 3A and 3B).

As used in this specification, the term "V-shaped" includes a V with a vertex point and a V with a "flattened" or "plateau" vertex. This will be further elaborated in the following paragraphs.

The movable track 20 must be movable within the casing 10 to enable clamping of the portion of the natural tree pole received within the receptacle 40, against the static track 30. The movable track 20 comprises a top portion 21, a pair of spaced apart side portions 22 and a base portion 23, with the top and side portions 21, 22 being planar and the base portion 23 being a generally inverted V. The two inclined faces of the inverted V contact against portions of the natural tree pole received within the receptacle 40, in use.

In an embodiment, the inclined faces of the inverted V meet at a vertex point. In another embodiment, the apex portion of the inclined faces of the movable track base 23 are spaced apart such that a flat-top channel or "plateau" is defined therebetween. This "flat-top channel" or "plateau" embodiment is particularly preferred as it allows for a more economical compact dimensional configuration of the casing 10. As can be appreciated by a person skilled in the art, the casing 10 would need to be of greater height in order to accommodate the embodiment where the two inclined faces of the movable track 20 meet at a vertex point as opposed to the preferred flat-top channel embodiment.

The static track 30 of the connector of this invention must be static within the casing 10 and may be integral with the casing 10 or separately provided from the casing 10. Whether integral with or separately provided from the casing 10, the two inclined faces of the V-shaped static track 30 contact against portions of the natural tree pole received within the receptacle 40, in use.

When integral with the casing 10, the static track 30 is defined by the base 13 of the casing 10. As mentioned above, the casing 10 could be five sided with the top and side portions 11, 12 of the casing 10 being planar and the base portion 13 comprising two inclined faces that taper to a point i.e. a V-shape that defines the static track 30 (e.g. Figures 8 and 10).

When separately provided from the casing 10, the static track 30 may comprise a pair of wedges (e.g. Figures 1, 2A and 2B). Each wedge is affixed to an opposing side of the casing base portion 13 so as to define a V-shaped track therebetween. The wedges may be sized and configured such that a "closed V" shaped track is defined therebetween or they may be spaced apart to define an "open V" shaped track with a flat-bottom channel defined between the inclined faces of each wedge.

Alternatively, the static track 30 may be an inverted version of the movable track 20 and comprise a base portion 33, a pair of spaced apart side portions 32 and a top portion 31, with the base and side portions 33, 32 being planar and the top portion 31 comprising a pair of inclined faces that taper to define a V-shaped track. The inclined faces of the V could meet at a vertex point or be spaced apart such that a flat-bottom channel is defined therebetween.

As with the movable track 20, both of the "flat-bottom channel" embodiments of the static track 30 are particularly preferred as it allows for a more economical compact dimensional configuration of the casing 10.

The diamond-shaped receptacle 40 for receiving a portion of a natural tree pole comprises a first pair of inclined contact faces 41 (movable track 20) and a second pair of inclined contact faces 42 (static track 30). In use, the collinear points of contact between the first pair of inclined faces 41 and the natural tree pole are diagonally opposing to those between the second pair of inclined faces 42 and the natural tree pole. This results in a 45° inward radial force acting on the natural tree pole from each of the four sides of the receptacle 40 and ensures an even distribution of load stress when the movable track 20 is moved toward the static track, to clamp the pole against the static track 30 (e.g. Figures 3B and 4A). Such a uniform distribution of force also results in a balanced hoop stress about the circumference of the natural tree pole. Floop stress is the force exerted circumferentially (perpendicular both to the axis and to the radius of the object) in both directions on every particle in a cylinder wall. Imbalanced load stress and/or hoop stress can lead to structural weakening or structural failure of the natural tree pole.

The connector may also comprise a clamping mechanism 50 to actuate movement of the movable track 20 within the casing 10 and to lock in position the portion of the natural tree pole received within the receptacle 40. Importantly, the clamping mechanism 50 of the connector of this invention does not comprise any part or portion that penetrates into the natural tree pole. In fact, the clamping mechanism 50 of this invention does not directly contact any surface of the natural tree pole (e.g. Figure 3B).

The clamping mechanism 50 may comprise any suitable element that allows for the movable track 20 to be moved toward (and moved away) from the static track 30 to clamp the natural tree pole against the static track 30 and lock it in place within the receptacle 40. The element should be configured such that the clamping mechanism 50 can be actuated external to the casing 10. Such a clamping mechanism 50 mainly comprises an actuator element 51 anchored on a portion of the casing 10 and operatively connected to the movable track 20 to effect movement of the track.

In an embodiment (e.g. Figures 1, 3A and 3B) the actuator element 51 comprises a bolt that is receivable through a threaded hole 52 on the top portion 11 of the casing 10. The bolt 51 is operatively connected to the movable track 20 by way of a matching nut (not shown) on the top portion 21 of the movable track 20. The head of the bolt 51 is accessible above the casing top portion 11. Turning the bolt 51 clockwise or counterclockwise tightens or loosens the bolt 51 and causes the movable track 20 to be moved toward or moved away from the static track 30. Any suitable type of bolt can be used for this purpose.

Depending on the size (depth) of the casing 10, either one or more than one actuator element 51 may be provided. The actuator element(s) 51 should be located at a point(s) of longitudinal and lateral stability on the casing top portion 11 (and movable track top portion 21) such that the movable track 20 can be maintained generally level, during movement. In use, when the actuator element 51 of the clamping mechanism 50 is activated to move the movable track 20 toward the static track 30, the portion of the natural tree pole received within the receptacle is clamped and locked in position against the static track 30. The shape and configuration of the movable and static tracks 20, 30 (both being V-shaped tracks and disposed to be diametrically opposed) are such that the collinear points of contact between the movable track 20 and the natural tree pole are diagonally opposing to those between the static track 30 and the natural tree pole. The resulting 45° inward radial force acting on the natural tree pole from each of the four sides of the receptacle 40 ensures an even distribution of load stress caused by the clamping force and makes it possible to achieve a balanced hoop stress about the circumference of the natural tree pole.

Connectors of this invention can be made in a variety of sizes depending on the range of diameter (maximum to minimum) of the natural tree poles to be accommodated. The range of diameter of the natural tree poles to be accommodated by the connector or diametrical variance very much depends on the configuration of the movable and static tracks, whether the movable and static tracks are in the "sharp" configuration or the "plateau" or flat channel configuration.

As mentioned in earlier sections of the detailed description, the movable track can be an inverted V that meets at a vertex point and the static track can be a "closed V" or a pair of inclined faces that taper to a vertex point. This is the "sharp" configuration, as schematically shown in Figure 8A. Alternatively, the movable track can have a "flat-top" channel configuration and the static track an "opened V" shaped track or "flat-bottom" channel configuration. This is the "plateau" or flat channel configuration, as schematically shown in Figure 8B.

For example, as seen in Figure 8A, a connector having a movable track in the "sharp" configuration can be sized to accommodate a natural tree pole having a diametrical variance of 1.414:1.

On the other hand, as seen in Figures 5A to 5D, a connector having a movable track in the preferred "flat-top channel" configuration could be sized to receive natural tree poles having a diametrical variance of up to 1.5:1 (maximum to minimum ratio), and preferably, a diametrical variance of 1.25:1. An exemplary calculation using bamboos is provided below to demonstrate how the inventors arrived at the above- mentioned diametrical variance (maximum to minimum ratio) for connectors of this embodiment.

A set of wedges were arranged (each wedge being a 45°-45°-90° right isosceles triangle) to clamp a bamboo with the smallest diameter (0s). The height of the wedges (X0s) and the gap (Y0s) between the wedges equals the smallest bamboo diameter (0s). This is shown in Figure 6A.

While maintaining the distance Z, the upper wedges of the same set of wedges were subsequently moved to clamp a bamboo having the largest diameter (0/.). In this scenario, Z is actually 0 as shown in Figure 6B.

A calculation for the diametrical variance was then made in view of two hypothetical scenarios.

Firstly, in the scenario where X was taken as 0.4 and Y was taken as 0.2 i.e. 0.4-0.2- 0.4 configuration). A formula for 0L as a function of 0s was developed, as shown below.

0L = 0.40s + V0s + 0.40s = 0.80s + V0s V = 0.4143 (calculated by AutoCAD program)

0L = 0.40s + 0.41430s + 0.40s = 1.21430s

The above equation implies that the maximum diameter of bamboo that can be received within the connector of this invention having a 0.4-0.2-0.4 configuration is 21.43% larger than the smallest fitted diameter. In other words, if the smallest diameter is 10 cm, then the largest diameter is 12.143 cm. The diametrical variance that can be accommodated in a connector of this invention having a 0.4-0.2-0.4 configuration can thus be nominally designated as 1.2:1.

In the second scenario, X was taken as 0.35 and Y was taken as 0.3 i.e. 0.35-0.3- 0.35 configuration (wedge height is 0.350s and gap is 0.30s). Value of V as calculated by the AutoCAD program is, V = 0.4138.

0L = 0.350s + 0.41380s + 0.350s = 1.11380s

The above equation implies that the maximum diameter of bamboo that can be received within the connector of this invention having a 0.35-0.3-0.35 configuration is 11.38% larger than the smallest fitted diameter. If the smallest diameter is 10 cm, then the largest diameter is 11.138 cm. The diametrical variance that can be accommodated in a connector of this invention having a 0.35-0.3-0.35 configuration can thus be nominally designated as 1.1:1.

The exemplary calculations provided in the preceding paragraphs show that if the value of the gap is closer to that of the wedge height, the diametrical variance that can be accommodated by the connector becomes smaller.

Following on from the above observations, the inventors calculated the internal dimensions of the casing 10 of a connector of this invention having a 0.35-0.3-0.35 configuration. Figure 7A shows the dimensions of such a connector for accommodating bamboos within the 70 to 78 mm diameter range. Figure 7B shows the dimensions of such a connector for accommodating bamboos within the 90 to 100 mm diameter range.

A further variation of the "sharp" configuration can be seen in Figure 8C, where the movable track can be an inverted V that meets at a vertex point and the static track can be a "closed V" or a pair of inclined faces that taper to a vertex point. In this variation, the movable and static tracks are configured such that a flat plateau is formed on either side of the inclined faces of the tracks. Two embodiments of this variant are shown in Figures 8D and 8E, an "open" variant (Figure 8D) and a "closed" variant (Figure 8E). The diametrical variance of natural tree poles that can be accommodated by a connector in this variation can be calculated as follows.

Figure 8D shows that the distance from the center 0_L to A, or O_lA = radius of the largest natural tree pole = O.50L Since ACDOL is a square, OLA = AC

As per Figure 8E, the diameter of the smallest natural tree pole, 0s = AC AC = OLA = O.50_L 0s = O.50L 0L = 20s

Hence, the diametrical variance of a natural tree pole that can be accommodated by a connector in this variant configuration is 2:1.

The dimensions of each of the constituent elements (casing 10, movable track 20, static track 30) of the connector can be sized according to the diametrical variance of the natural tree pole to be accommodated. Calculation of the dimensions of an exemplary casing 10 (and static track 30) and movable track 20 of a connector with reference to the maximum diameter of a natural tree pole to be accommodated can be seen in Figures 9A and 9B and in Table 1 below.

Table 1: Calculation of the dimensions of an exemplary casing (and static track) and movable track of a connector of Figure 8.

The geometric parameters (e.g. diameter, thickness, area, moment of inertia) of a natural tree pole can vary greatly along its length. This inherent geometric variation of the poles has a significant effect on their structural behavior with differences in maximum vertical displacements of up to 14%¹. To cater for such variance in vertical displacement, the depth of the casing of the connector of this invention should be increased corresponding to an increase in the moment of inertia of the natural tree pole received within the receptacle.

The natural tree poles to be joined with the connector of this invention can comprise hardwoods, softwoods or woody grass species. Each of these types of natural tree pole derivatives have distinctly different microstructures.

Hardwoods and softwoods typically have vascular bundles (xylem, phloem) that form concentric rings. Hardwoods comprise vessel members, fibres and parenchyma (matrix) with the proportion of constituent cell-types being species dependent. Vessel members and fibres are always present and axially oriented. Softwoods comprises tracheids and parenchyma, with the predominant constituent being tracheids, which are mainly axially oriented. Axial parenchyma is present in only certain softwood species, but radial parenchyma is always present.

On the other hand, woody grass (e.g. bamboo) have scattered vascular bundles with each bundle encapsulated within a bundle sheath. The scattered vascular bundles are surrounded by parenchyma. The structural strength and hardness of woody grass is due to clusters of heavily lignified tracheids and fibers associated with the vascular bundles.

The parenchyma is known to disperse compression forces whereas the vascular bundles disperse tension forces. Different species of natural tree poles have different microstructure composition i.e. different ratio of vascular bundles versus parenchyma. Due to this, different species of natural tree poles will have different geometric parameters and thus, different structural behaviors.

When developing a joinery system, woody grass such as bamboo, pose particularly unique challenges. Bamboo geometry can be described as a long tapered hollow cylinder, with intermittent transverse membranes along its axis, known as nodes. Although these geometric characteristics increase bamboo efficiency as a structural element due to the high strength -to-weight ratio, the same characteristics pose challenges due to the tapering diameter, randomly distributed nodes along its length, section properties varying along the length of the pole, and a generally inherent lack of straightness in a bamboo pole.

The dimensions of each of the casing 10, movable track 20 and static track 30 of the connector of this invention can be easily adjusted to accommodate all of the above- stated differences.

All of the main constituent elements of the connector can be made of any material suitable for use in structural constructions.

The casing 10, movable track 20 and static track 30 can be made of the same material. Alternatively, each element or a combination of elements of the connector can also be made of different materials. For example, all of the casing 10, movable track 20 and static track 30 could be made of wood or the casing 10 having an integral static track 30 could be made of metal with the separately provided movable track 20 made of wood, or the casing 10 could be made of wood with the movable and static tracks 20, 30 made of metal.

As seen in Figures 1, 2, 3, 5 and 10A, the casing 10, the movable track 20 and/or the static track 30 could be solid elements that are made of wood, plastic or metal. In an alternative embodiment (Figures 10B, 11A and 11B), the casing 10, the movable track 20 and/or the static track 30 could be hollow elements molded from metal sheets, for example, galvanized steel sheets.

The connector of this invention can be used as a singular unit or modularly in a multiple-connector combination joint.

As a singular unit, the connector can be directly bolted to a base plate to form an upright column or an inclined column, as shown in Figures 12A and 12B.

Alternatively, the single connector can be vertically displaced from and connected to the base plate via a series of support struts, as shown in Figure 13. This "raised" configuration allows for increased airflow underneath (and within) the connector, thus, preventing the accumulation of moisture inside the connector and increasing durability of the natural tree pole held therewithin. In line with this embodiment, it is also conceivable that the sides of the casing 10 of the connector can be additionally provided with a plurality of holes for easy drainage of water or rain.

When used modularly, the multiple-connector combination joints can be onedimensional, two-dimensional or three-dimensional joints. Figures 14A to 14D shows exemplary configurations of two- and three-dimensional joints such as 3D- xyz, 2D-yza, 3D-xyza and 2D-xy.

In certain configurations of combination joints, an additional modular joint adaptor 60 can be optionally added, e.g. see Figures 14A, 14B and 14D. Each connector unit and modular joint adaptor 60 in such combination joints can be fixed together by any suitable means.

The modular joint adaptor 60 can also be of a circular configuration so as to enable formation of a combination joint of multiple connector units to hold together roof hip rafters and/or to form a roof apex, as shown in Figure 15.

Alternatively, in other configurations of combination joints, each connector unit can be directly fixed together (Figure 16A) or can be separately bolted onto a base plate (Figure 16B), or both (Figure 16C).

The combination joints are highly versatile and can be used for temporary structural frames or permanent heavy structures. For example, as seen in Figure 17, several two-dimensional and three-dimensional combination joints are utilized to form a structural frame for a temporary disaster relief tent. When used for a more permanent or heavy structure (e.g. car porch) as seen in Figure 18, connectors of this invention having casings 10 made of metal can be bolted to concrete stumps.

The connectors of this invention can also be used to form a brace for structural constructs, such as, an L-shaped brace as per Figure 19A or a T-shaped brace as per Figure 19B. When used in such a "brace configuration", the connectors can be permanently or removably fixed together by way of a connecting plate or rod. EXAMPLE

The following Example illustrates various aspects of a natural tree pole connector of this invention. This Example does not limit the invention, the scope of which is set out in the appended claims.

Example: Models of Connectors with 1.25:1 Diametrical Variance This example illustrates the various size configurations of a casing of the connector of this invention for receiving bamboo poles having a diametrical variance of 1.25:1 (maximum to minimum ratio).

Twelve species of bamboos² found in Malaysia were identified as suitable for commercial use. Due to variations in microstructures across these twelve species, each bamboo species has different geometric parameters and different structural behaviors.

As shown in Table 2 below, twelve different size configurations of the connector casing were made to accommodate these variations.

Table 2: Dimensions of twelve models of connectors for accommodating diametrical variance (maximum to minimum) of 1.25:1. The above Example illustrates the ease with which the connector of this invention can be easily adapted to accommodate the diametrical variances of a myriad of species of natural tree poles. All directional statements such as top, side, base, bottom, internal and/or external, made here are relative to the orientation of the connector, in use.

As will be readily apparent to those skilled in the art, the present invention may easily be produced in other specific forms without departing from its scope or essential characteristics. The present embodiments are, therefore, to be considered as merely illustrative and not restrictive, the scope of the invention being indicated by the claims rather than the foregoing description, and all changes which come within therefore intended to be embraced therein.

References

Rodolfo et. al. (2019): Digital Analysis of the Geometric Variability of Bamboo Poles in Bending. MATEC Web of Conferences 275, 01007 (2019).

²Azmy Hj. Mohamed and Abd. Razak Othman (1991): Field Identification of Twelve Commercial Malaysian Bamboos. FRIM Technical Information No. 25. Forest Research Institute Malaysia, Kepong, Malaysia. 12pp.

Claims

1. A natural tree pole connector, said connector comprising: a casing (10); a movable track (20) and a static track (30) within said casing (10); each of said movable and static tracks (20, 30) comprising a V-shaped track and disposed diametrically opposite each other such that the movable and static tracks define a diamond-shaped receptacle (40) for longitudinally receiving a portion of a natural tree pole; said movable track (20) being movable to clamp the portion of the natural tree pole received within said receptacle (40), against the static track (30); wherein, the shape and configuration of said movable and static tracks (20, 30) are such that the collinear points of contact between said movable track (20) and the natural tree pole are diagonally opposing to those between said static track (30) and the natural tree pole, resulting in a 45° inward radial force acting on the natural tree pole from each side of said receptacle (40).

2. The connector of claim 1 wherein said casing (10) comprises a top portion (11), two side portions (12) and a base portion (13).

3. The connector of claim 1 or claim 2 wherein said casing (10) is rectangular in shape.

4. The connector of any one of claims 1 to 3 wherein said movable track (20) comprises a top portion (21), a pair of spaced apart side portions (22) and a base portion (23), with said top and side portions being planar and said base portion being an inverted V.

5. The connector of any one of claims 2 to 4 wherein said static track (30) comprises a pair of wedges, each wedge affixed to an opposing side of said casing base portion (13) so as to define a V-shaped track therebetween.

6. The connector of claim 1 or claim 2 wherein said static track (30) comprises the base (13) of said casing (10).

7. The connector of any one of the preceding claims, wherein said connector further comprises a clamping mechanism (50) for effecting movement of said movable track (20) and locking in position the portion of the natural tree pole received within said receptacle (40).

8. The connector of claim 7 wherein said clamping mechanism (50) comprises an actuator (51) anchored on said casing (10) and operatively connected to said movable track (20).

9. The connector of claim 8 wherein said actuator (51) is located at a point of longitudinal and lateral stability on said casing top portion (11) such that said movable track (20) can be maintained generally level, during movement.

10. The connector of any one of claims 7 to 9 wherein said clamping mechanism (50) comprises a bolt (51) receivable through a threaded hole (52) on said casing top portion (11), said bolt operatively connected to a nut on said movable track top portion (21), wherein tightening or loosening said bolt effects movement of said movable track (20).

11. The connector of any one of the preceding claims, said connector sized to receive natural tree poles having a diametrical variance of up to 2.0:1 (maximum to minimum ratio).

12. The connector of any one of the preceding claims, said connector sized to receive natural tree poles having a diametrical variance of 1.5:1 (maximum to minimum ratio).

13. The connector of any one of the preceding claims, said connector sized to receive natural tree poles having a diametrical variance of 1.25:1 (maximum to minimum ratio).

14. The connector of any one of the preceding claims wherein said casing (10), said movable track (20) and said static track (30) are made of the same material.

15. The connector of claim 14 wherein said casing (10), said movable track (20) and said static track (30) are made of wood.

16. The connector of claim 14 wherein said casing (10), said movable track (20) and said static track (30) are made of plastic.

17. The connector of claim 14 wherein said casing (10), said movable track (20) and said static track (30) are made of metal.

18. The connector of any one of claims 1 to 13 wherein said casing (10), said movable track (20) and said static track (30) are made of different materials.

19. The connector of any one of claims 14, 17 or 18 wherein said movable track (20) and said static track (30) are molded from a metal sheet.

20. The connector of any one of claims 14, 17 or 18 wherein said movable track (20) or said static track (30) are molded from a metal sheet.

21. A combination joint comprising multiple units of the connectors of any one of the preceding claims.

22. The joint of claim 21 further comprising a modular joint adaptor (60).

23. The joint of claim 21 or claim 22 wherein said joint is a one-dimensional joint.

24. The joint of claim 21 or claim 22 wherein said joint is a two-dimensional joint.

25. The joint of claim 21 or claim 22 wherein said joint is a three-dimensional joint.