| WO/2000/061893 | KNEE BRACE BRACKET FOR TILT-UP CONSTRUCTION |
| JP02024462 | METHOD FOR PLANTING SNOW-MELTING SUPPORT WIRE |
| WO/1988/003593 | POLE REINFORCEMENT SYSTEM |
SUAREZ AYA, Victor Manuel (Carrera 76 # 131-21, Casa 11Bogotá Colombi, Bogotá ., 11001, CO)
GOMEZ PORRAS, Armando (Carrera 68 # 180-80, Casa 4Bogotá Colombi, Bogotá ., 11001, CO)
MURCIA QUIJANO, Fernando (Carrera 56A # 148-87, Bogotá ColombiaBogotá, 11001, CO)
TORRES VEGA, Robert Camilo (Calle 169 B # 75-73, Casa 94Bogotá Colombi, Bogotá ., 11001, CO)
SUAREZ AYA, Victor Manuel (Carrera 76 # 131-21, Casa 11Bogotá Colombi, Bogotá ., 11001, CO)
GOMEZ PORRAS, Armando (Carrera 68 # 180-80, Casa 4Bogotá Colombi, Bogotá ., 11001, CO)
MURCIA QUIJANO, Fernando (Carrera 56A # 148-87, Bogotá ColombiaBogotá, 11001, CO)
| CLAIMS 1. A temporary safety support for wooden poles characterized by comprising two sections, a superior one and an inferior one assembled to each other, wherein the superior section of said support is formed by a clamp attached by three connectors to three tubular arms from superior section, and inferior section formed by a clamp attached by three connectors to three horizontal tubes, each of them is attached to a double connector, which is in turn connected to a tubular arm from inferior section, and to a socket and ball joint axis, said socket and ball joint is supported in a basket attached to a shoe having holes by which it is fixed to the ground, wherein the assembly of superior section and inferior section of the support is made by inserting one of the ends of tubular arms of inferior section inside one of ends of tubular arms of superior section, obtaining a structure comprising three tubular arms with a 120° angle each other, and wherein the superior clamp is adjusted to a variable height in the pole, whereas the inferior clamp is located at ground level . 2. The support of claim 1 further characterized because tubular arms in both superior and inferior section have one smooth end and the other end with a male thread, and said tubular arms are assembled to each other through the smooth ends . 3. The support according to any of preceding claims, wherein the smooth ends of tubular arms both in superior and inferior section have each one separated holes allowing the adjustment of different heights of the support once assembled . 4. The support according to claim 3, wherein adjustment of height in each arm is made by a metallic pin. 5. The support according to any of preceding claims, wherein the smooth end of each tubular arm from superior section has a plastic bushing improving assembly with the tubular arm from inferior section. 6. The support of claim 1, wherein both clamp from superior section and from inferior section are equal, and comprise three plates, two of them are equal to each other and separated by a third central plate different from the other two. 7. The support of claim 6, wherein the equal plates forming clamps comprise two hinge type connectors, one horizontal and one vertical, and a perforated sheet perpendicular to the axis of the plate. 8. The support of claim 5 wherein the central plate of clamps comprises in its ends, two sheets perpendicular to the plane of the plate, supporting two perforated flanges, and in the centre, a vertical hinge type connector |
WITH BREAKING RISK
BACKGROUND OF THE INVENTION
The present invention refers to a temporary support for wooden poles giving safety and protection to workers which must carry out maintenance works on the top of the pole.
In rural electric networks there are many areas of difficult access wherein the only option is the use of wooden poles which are lighter and easy to transport than metallic or concrete poles. Additionally, said wooden poles are cheaper making them a profitable and technically suitable alternative for networks in this type of areas.
However, environmental conditions and growth of microorganisms deteriorate said poles, especially in the air-ground point (lower part of the pole, on the embedding line) , causing them to decay. This happens even when previous treatments are made on poles with chemical substances to immunize the wood against microbial attack. Said deterioration is reflected in the decrease in diameter of the pole, and thus, reduction in mechanical properties thereof .
Thus, by increasing the number of years of service of the pole, possibility also increases to be deteriorated and which may be broken when withstanding an additional strength (such as for example, tilt caused by wind) . Decay of poles in the air-ground line is usually not easy to be detected at sight, and then it is not possible to be sure about the conditions of a pole with a quick evaluation, which has caused serious work accidents because of fracture of the pole at the moment when a worker is in the top thereof .
Given the great number of this type of poles installed and geographic difficulties, replacement of deteriorated poles would produce high costs and interruptions in the electric supply. For these reasons, in general, alternative of repairing poles is preferred than replacing them.
There exist different publications in the technical field of the invention disclosing reinforcement alternatives for wooden poles, being the first of them, treatment with epoxy resins, fibers and/or fillings completing the defects of the structure and restore the damaged part (Naval Facilities Engineering Command, Alexandria, Virginia "Inspection , Maintenance and Procurement Procedures for Wood Poles" NAVFAC MO-312.3, September, 1992).
Additionally, anchor guy-type structures has been used securing the poles to the ground permanently by using metallic cables (guy wires) , as well as structures known as "reinforcement stubs" acting as fixed and side support to the poles (US 5,383,749) . In other hand, documents exist disclosing mechanical reinforcements such as concrete collars located in the inferior part of the pole (CA1250731), coatings with a rigid sleeve containing a hardenable material such as cement covering both the embedded part and the part on the ground of the base of the pole (US 4,644,722), metallic reinforcements interlocked in both sides of the pole, and longitudinal metallic reinforcements formed by a series of elongated parts arranged around de diameter of the pole, which are adjusted by a hydraulic mechanism to the shape of the pole (US 4, 991, 367) . All these possibilities constitute permanent reinforcements that despite increasing useful life of the pole require work time and additional costs for the servicing company.
Additionally, considering that in the rural area there are about 35.000 poles with high decay degree, this implies that no maintenance to the electric line may be done without carrying out a previous reinforcement of each of these poles, producing a high cost and excessive waiting time for maintenance works .
Added to the above, as mentioned before, a rapid visual inspection of the state of the pole usually does not allow identify precisely its decay degree, then there may exist many damaged poles which would not be evaluated as priority for permanent reinforcement and which, however, constitute a potential risk at the moment of subjecting to additional tensions such as climbing or stay of a worker on the top.
As a consequence of the above, only in the Department of Cundinamarca, Colombia, during the last 4 years, there has happened 8 accidents of workers carrying out maintenance on wooden poles which were not apparently very damaged, which fractured because of the additional tension caused by the weight of the worker. From these accidents, 2 were mortal, 2 caused permanent partial disability injuries, for hip injury and spinal cord, and other 4 caused temporary partial disability, for multiple fractures. Also, there are records about 25 serious accidents in last 4 years because of falling of workers from wooden poles in other regions of the country. Therefore, there is a need of a structural reinforcement system for wooden poles to be temporary, which may be easily transported by a worker, installed in few minutes even in difficult access areas and to give sufficient support to avoid fracture of the pole at the moment when the worker is carrying out works on the top of the pole.
BRIEF SUMMARY OF THE INVENTION
The present invention solves above exposed problems by providing a light, easy to transport system which may be installed by the worker in very short time, and providing sufficient support so that the wooden pole withstands without fracture the tension excess produced by the weight of the worker on the top thereof, regardless the deterioration degree said pole has.
Safety support provided by the present invention is constituted by a metallic structure which may be assembled, composed by two sections, a superior one and an inferior one, being superior section constituted by three tubular shaped arms, which are connected to a clamp, and the inferior section by a clamp attached to three horizontal tubes, a double connector and three tubular shaped arms.
Once assembled, the support of the invention gives a tripod-like structure wherein the clamp of the inferior part is arranged at ground level and the clamp of the superior part is installed at variable height according to the length of the pole on which works will be carried out.
For installation and use, the support of the invention is anchored to the ground by stakes passing through holes present in some plates or fastening shoes, which are attached to each tubular arm of the inferior section of the support. Said shoes may be adapted to any type of ground regardless geographic conditions it has.
Surprisingly, the support of the invention despite of being light, easy to assembly and may be installed in few minutes, provides a superior resistance to the pole, regardless its deterioration degree, allowing offer safety to the worker during works on the top of the pole.
Additionally, by being a temporary reinforcement support, it can be used and dismounted as many times as necessary, then it does not imply additional costs of the distribution network, neither delay in carrying out maintenance works due to the state of poles.
BRIEF DESCRIPTION OF FIGURES
Figure 1 shows a perspective view of both sections forming the safety support of the invention.
Figure 2 corresponds to perspective and side views of the support of the invention once assembled.
Figure 3 shows the location and characteristics of the plastic bushing present in superior tubular arms in an embodiment of the invention.
Figure 4 corresponds to the superior view of the safety support of the invention already assembled.
Figure 5 shows the support of the invention installed at its maximum and minimum height. Figures 6a and 6b correspond to the detail of clamps present both in superior and inferior section of the support of the invention, and to the plates forming it.
Figure 7 illustrates the way how superior clamp is attached to the tubular arms.
Figure 8 is the detail of attachment of each arm form inferior section of the support to the socket and ball joint and fastening shoe.
DETAILED DESCRIPTION OF THE INVENTION
Upon carrying out maintenance works on the distribution network, many poles fracture at ground level due only to the tension and additional movements produced by climbing and stay of a worker on the top of the pole.
The present invention provides a temporary support for structural reinforcement of wooden poles offering safety to the worker when carrying out maintenance on the top of the pole, regardless the deterioration said pole may have.
Said support of the invention is constituted by two sections, a superior one (A) and an inferior one (B) , Figure 1, which are assembled together at the moment of using the support on a pole. Once assembled, the support of the invention provides a tripod-like structure as that shown in Figure 2, which is formed mainly of two clamps, a superior one (1) and an inferior one (2) and three tubular arms formed due to the assembly of arms in the superior (3) and inferior (4) sections. Additionally, the support of the invention has three horizontal tubes (5) attached to the inferior clamp (2) serving as a bridge with the arms of the inferior section (4) and three shoes (6) allowing fixing to the ground. Said shoes serve as support for a socket and ball joint (10) attached to a double connector (8) receiving arms from the inferior section (4), the axis of the socket and ball joint (9) and the connector (7) supporting horizontal tubes (5) .
In general, each of the clamps present in the support of the invention has two kinds of hinge type connectors, a horizontal one (12) allowing attachment of parts of the clamp and another vertical (13) making possible the attachment with tubular arms of superior section (3) in the superior clamp (1) or with horizontal tubes (5) in the inferior clamp (2) . For said attachment between tubular arms of superior section (3) and the superior clamp (1) a connector (7) is used, which has a perforated flange designed to provide a hinge type union and a female thread receiving said tubular arm.
Thus, tubular arms of superior section (3) have in one end a male threaded allowing attachment thereof to the connector (7), whereas the other end of said tubular arm is smooth to allow assembly with tubular arms of inferior section (4) of the support. Similarly, tubular arms of inferior section (4) have one smooth end and the other with a male thread, allowing this last the attachment to the double connector (8) . Assembly between arms of superior (3) and inferior (4) sections is made by introducing the smooth end of tubular arm of inferior section (4) into de smooth end of tubular arm of superior section (3) . In a preferred embodiment of the invention, a concentric tube or plastic bushing (24) is used inserted into the smooth extreme of the tubular arm of superior section (3) to improve adjustment with the tubular arm of inferior section (4) avoiding friction, as observed in Figure 3. Said plastic bushing is usually made of nylon, preferably polyamide 6, or polyamide 66, and has a length corresponding to 16 to 18% of total length of the superior tubular arm (3) .
In other hand, inferior clamp (2) is attached to the three horizontal tubes (5) by connectors (7) . Said horizontal tubes (5) have both male threads ends allowing their attachment to two connectors (7), one of which is attached to the vertical hinge connector (13) of the inferior clamp, and the other is attached to the double connector (8) . Said double connector (8) also receives the axis (9) of a socket and ball joint (10) assembled on a shoe (6) . This shoe (6) has two holes allowing fixing of the support to the ground.
Closing of superior (1) and inferior (2) clamps is made by a stud bolt (15) . Hinge type union of both sections of clamps and connectors with clamps, or connectors each other is made by pins (19) .
Figure 4 corresponds to the superior view of the support of the invention assembled, and shows how three arms forming said support are forming an angle of 120° each other.
As mentioned before, when assembling sections A and B of the support of the invention, smooth ends of tubular arms of inferior section (4) are inserted inside the smooth ends of tubular arms of superior section (3) . Said smooth ends of tubular arms in both superior (3) and inferior (4) sections have holes, separated about 7 cm to each other, allowing a variable adjustment of the height of safety support, according to the length of the pole wherein said support well be installed, as shown in Figure 5. Also, plastic bushing (24) present in Figure 3 has the same holes. To fix length of each arm a thin metallic pin (11) is used, which is attached to a welded chain to the tubular arm of superior section (3) , which passes through mentioned holes from both tubular arms (3), (4) and from the plastic bushing (24 ) .
These holes also allow adjustment of a different length for each arm of the assemble support, according to the slope of the ground wherein said support is installed.
Once support of the invention is assembled, the clamp of inferior section (2) is arranged on the pole at ground level, whereas superior clamp (1) is adjusted on the pole at a variable height. Maximum height of the support of the invention once assembled is about 230 cm, preferable between 230 and 220 cm, and minimum height is from about 80 cm, preferably between 80 and 100 cm.
In other hand, both the superior clamp (1), and the inferior one (2) are constituted similarly, as shown in Figure 6a. Said clamps are formed from the metallic curve plates, which joined form a circumference. Two of these plates are equal to each other (21), and are separated to each other in one of their ends by the third central plate which is different (22) . Figure 6b shows the plates (21) and (22) forming the clamps of the support of the invention. Both equal plates (21) have, in one end, a horizontal hinge type connector (12), which allows attachment to the perforated flange (23) of central plate (22), by a pin (19). In the other end, equal plates (21) have a perforated sheet (14) perpendicular to the surface of the plate, which allow closing the clamp because of the stud bolt (15) . Mentioned perforated sheet (14) has a metallic bushing (20) to house the stud bolt (15) .
Additionally, plates (21) have in their central part a vertical hinge type connector (13) which allows attachment to connectors (7), as discussed below.
In other hand, central plate (22) has in both ends two sheets perpendicular to the plane of the plate, each of which supports a perforated flange (23) allowing the hinge type union with plates (21), by the horizontal hinge connector (12), by means of a pin (19). In the centre of said central sheet (22) there is a vertical hinge type connector (13) which allows union to the connector (7) .
Both horizontal (12) and vertical (13) hinge type connectors, as well as perforated flanges (23) , are attached to the surface of plates (21) and (22) by a set of countersunk head screws (16) . In a preferred embodiment of the invention, a set of four countersunk head screws is used for each of these attachments.
Figure 7 illustrates the superior clamp (1), attached to tubular arms of the superior section (3) . As exposed before, each of three plates forming the clamp has a vertical hinge type connector (13) receiving the perforated flange of a connector (7) and by a pin (19) they form a hinge type union. Perpendicular perforated sheets (14) allow opening the clamp for installation on the pole, and after said installation closing of clamp is made by a stud bolt (15) .
For the case of the inferior clamp (2), vertical hinge type connectors (13) are attached to connectors (7) of horizontal tubes (5) , which are attached by their other end to another connector (7) attached by a pin (19) to a double connector ( 8 ) .
Configuration of said double connector (8) is illustrated in Figure 8, showing how the double connector (8) receives in the superior part the male thread of one of inferior tubular arms (4), in the side part to the flange of a connector (7) attached to each of horizontal tubes (5), and in the inferior part to a socket and ball joint axis (9) . Unions of double connector (8) with said connector flange (7) and with the socket and ball joint axis (9) are made by a pin (19).
In other hand, the ball and socket joint axis (9) is attached to the ball and socket joint (10), which is housed in a basket (17) joined to a shoe (6) which has two holes
(18) allowing fixing of the support to the ground. This fixing is made by stakes, which may have a variable length according to the needs of the ground. Preferably, holes
(18) are not completely perpendicular to the surface of the shoe but they have a tilt angle avoiding easy removal of stakes .
Thanks to this shoe and socket and ball joint system, the support of the invention may be installed in any type of ground, regardless its slope or geologic constitution. In a preferred embodiment of the invention, each tubular arm of the superior section (3) has a diameter between 60 and 65 mm, whereas tubular arms of inferior section (4) have a diameter between 35 and 40 mm. In this embodiment, both superior (3) and inferior (4) tubular arms have a length of about 120 cm.
Also, in an embodiment of the invention, clamps have a diameter between 16 and 32 centimeters, preferably of 20 cm or 31 cm.
In a preferred embodiment of the invention, the support is made of an aluminum alloy, whereas pins (19), thin pins (11), axis of the socket and ball joint (9) and socket and ball joint (10) are made of steel.
In an additional embodiment, the support is of aluminum 6063-T5, and pins (19), thin pins (11), axis of the socket and ball joint (9) and socket and ball joint (10) are made of polished round steel (silver steel 3030).
Also, in a preferred embodiment of the invention, weight of the support completely assembled is preferably inferior to 20 Kg, more preferably between 15 and 17 Kg. Therefore, weight of each section (A) and (B) forming said support is preferably inferior to 10 Kg, more preferably between 7.5 and 8.5 Kg. This allows the support of the invention to be easily transported by a worker, even in very isolated areas .
An additional advantage of the support of the invention is that it may be assembled in a very short time. In a preferred embodiment of the invention, the support is assembled in 10 minutes or less, preferably in 9 minutes and more preferably in 8 minutes.
This short installation time allows the worker to use the support of the invention before carrying out maintenance works on the top of the pole, without causing excessive delay in his job. Also, said support of the invention may be easily uninstalled at the end of the maintenance, leaving thus the support ready to be used again as required .
Assembly of the support of the invention may be made in different ways, but it is preferably to first install the inferior section clamp (2) around the pole at ground level, fixing to the ground subsequently the shoe (6) attached to each arm by driving two stakes. Subsequently, the superior section clamp (1) is open and installed around the pole at desired height, so that it is totally perpendicular to the longest axis of said pole. After this, arms of inferior section (4) are inserted inside arms of the superior section (3) , adjusting height of each arm as necessary and fixing said height by the thin metallic pins (11) .
FIELD TESTING
As mentioned before, wooden poles, despite of having being immunized previously, suffer from degradation alter certain service time. Although many times deterioration is not detectable at sight, a detailed inspection may disclose the damage caused to the structure of the pole. Based on this damage, some rating scales of deterioration degree of poles has established, in relation to the type of treatment necessary for their recovery (Morris Carreno, Paez Riano, Postratamiento a postes de madera levantamiento, catastro y diagnostico de las redes de media y baja tension (mt y bt) en servicio involucradas" XII Congreso Mundial Forestal, Quebec, Canada, 2003) :
TO: Decay lower to 5mm of difference in diameter.
Tl : Decay higher than 5mm of difference in diameter.
T2 : Internal decay and any diameter difference.
T3 : Damaged pole; it is diagnosed as pole for replacement due to high deterioration degree thereof.
In general, within the technical field of the invention it has been established that for a wooden pole to be suitable for distribution Networks service it should be guaranteed a breaking strength as follows:
• Light pole (between 565 mm and 920 mm minimum circumference at 2m from the base and 420 mm on the top) : 500 kg.
• Heavy pole (between 645 mm and 1 005 mm minimum circumference at 2m from the base and 60 mm on the top) : 800 kg.
(Classification according to "Reglamento Tecnico De Iluminacion y Alumbrado Publico . RETILAP" (Technical regulations for Public Lighting) Ministry of Mining and Energy, Republic of Colombia, August 2009, pages 77 to 79)
In this aspect, applicant has found surprisingly that regardless the decay degree of a pole, TO to T3, by using the support of the invention, a significant increase in breaking tension of said pole, even superior to 100% as proved in the following field tests.
1. Breaking strength.
To determine breaking strength of a pole on which support of the invention has been installed, the pole was subjected to perpendicular tension to its longest axis in similar way as established in standard ASTM D 1036 - 99.
Thus, a pulling line was tied 0,30m from the end of the pole by which a perpendicular force was applied to the higher axis of the pole. Between the turnbuckle and the pole, attached to the pulling line, a dynamometer was placed which registered the force applied.
The force was applied continuously and a constant speed, until breaking of the pole happened, registering the load when said breaking occurred
This assay was carried out with two light poles with different decay degree, first of them with a slight deterioration level, a Tl pole, which was treated previously and was in operation conditions.
The second of poles used in the assay was a high decay degree pole, classified as T3.
For the first of the poles, Tl, a breaking strength of 1600 Kg was obtained, with no deformation in structure of the support of the invention. In other hand, for pole with higher decay degree, T3, a breaking strength of 650 Kg was obtained.
This shows that the support of the invention provides a significant increasing in breaking strength of the pole, being said strength 3 times higher than that expected for a new pole in service for the case of Tl pole (under normal conditions expected breaking strength would be 500 Kg) . Also, strength obtained for a T3 pole (requiring to be replaced) was 1.3 times superior to said expected strength for a pole suitable for service.
This is a surprising fact because a light support such as that of the present invention allows increase significantly breaking strength of the pole, regardless deterioration it may have .
Thus, the support of the invention offers an improved safety to workers at the moment of carrying out maintenance works on the top of a pole, since installation of said support of the invention secures the pole, regardless deterioration degree thereof, to be under optimal conditions, and therefore, it will withstand completely the additional strength caused by the weight of the worker.
It is important to emphasize that mortal accidents occurred during maintenance works of distribution poles have happened only because of the strength produced by the weight of the worker on the top of the pole (maximum 100 Kg including weight of tools) , and only this strength has caused breaking of the pole. This is because most of wooden poles which are highly decayed in the base stay upright by the very Network, which acts as support, and once the pole is dismounted mechanical breaking is produced for just the additional weight and movement of the wires of the grid.
In this sense, the support of the invention provides a light, easy to assemble, of rapid installation and economic solution, and which allows protect life of workers, regardless geographic conditions or deterioration of the pole on which maintenance is required.
2. Mechanical Support Capacity under extreme conditions
To prove efficiency and mechanical strength of the support of the invention a test was carried out under extreme conditions using a pole 36 cm in diameter, 8 m length, and weighting 380 Kg, (almost twice thicker and heavier than those commonly used in the energy distribution network) . Said pole supported additionally a 100 Kg load on the top, simulating additional weight of a worker with tools.
The test was carried out with a not ground embedded pole to simulate a hypothetical "T3" pole, that is, such a high decay degree that the pole has totally lost its support in the ground.
The pole was placed vertically on the surface of the ground with the aid of a crane. Subsequently, the support of the invention was installed in the base of the pole and strength supplied by the crane was released, allowing the support of the invention to be the only mean the pole kept its vertical position.
Surprisingly, the support of the invention kept the structure of the pole totally vertical without requiring any additional aid and without suffering any type of deformation or damage.
Subsequently, by pulling lines tied 0.30 m from the superior part of the pole, oscillations were applied on the top up to 8 degrees, simulating movement by the presence of a worker or excessive wind. Even under these conditions, the support of the invention remained vertical to the ground without falling by overturning.
Above results prove that the support of the invention has surprisingly high strength offering improved stability to wooden poles regardless decay degree thereof, even in the hypothetical case wherein said pole would have totally lost its ground embedding.
This makes the support of the invention provide safety to workers requiring perform maintenance on wooden poles, without the need of carrying out previous evaluation and repairing of the pole, avoiding thus additional costs and time in maintenance works .
Despite a particular embodiment of the invention has been disclosed for illustrative purposes, it is recognized that variations and modifications to the embodiment are included in the scope of the application of the present invention.
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