GUSTAFSSON, Karl, Martin (Klingsbergsgatan 39, Norrköping, S-603 54, SE)
| Claims
1. Mast base, comprising a rigid body (10), intended to support a mast mounted thereon, and a plurality of supporting legs (16), serving to support said body upon a building, said supporting legs extending lateral- Iy from the body (10) in mutually diverging directions and being provided, at their outer ends, with supporting feet (17) by which they may rest upon said building, each supporting leg (16) comprising a lower arm (19), which, at its inner end, is connected to a lower portion of the body (10) and an upper arm (18), which, at its inner end, is connected to an upper portion of the body (10), said two arms (18, 19) of each supporting leg (16) extending in mutually converging directions towards the outer end of the supporting leg, where they are connected to each other, characterized in that the lower arms (19) of the supporting legs (16) are rigidly connected to the body (10) and in that the supporting feet (17) are adapted to be fixedly anchored to structural elements (33) of the body of the building. 2. Mast base according to claim 1, characterized in that it comprises only three supporting legs (16). 3. Mast base according to claim 2, characterized in that it comprises two supporting legs (16), placed in alignment with each other on opposite sides of the body (10), and a third supporting leg (16), extending from the body in a direction perpendicular to said two supporting legs.
A. Mast base according to any of claims 1 - 3, characterized in that, as seen in plan view, each supporting leg (16) has an individually adjustable length.
5. Mast base according to claim A, characterized in that the length of each supporting leg (16) is adjustable in steps.
6. Mast base according to claim 5, characterized in that the supporting feet (17) are mounted continuously adjustable on the supporting legs (16) for limited horizontal displacement of them relatively to the supporting legs.
7. Mast base according to any of claims 4 - 6, characterized in that each of the two arms (18, 19) of each supporting leg (16) comprises two elements (18A, 18B, 19A, 19B) which are mutually displaceable in a telescopic manner and lockable in different relative positions, the upper arm (18) of each supporting leg being pivotally connected to the body (10) at its inner end, while, at its outer end, it is pivotally connected to the lower arm (19).
8. Method for mounting a mast base according to any of the preceding claims upon a building, characterized by inserting anchor rods (36), serving to anchor the supporting feet (17) firmly to structural elements (33) of the body of the building, in bored holes (35) in said elements, intended to receive said rods therein, and fixing the anchor rods in said holes by injecting a hardeπable material (37) in the spaces between said rods (36) and the walls of said holes (35), and by se- curing the supporting feet (17) to the anchor rods (36) after the hardening of said material (37). |
Mast base and method for mounting it upon a building
The present invention relates to a mast base and especially to a base for an antenna mast suited to be placed upon a building having a flat roof.
More particulary, the invention relates to a mast base as above set forth comprising a ridig body, intended to support a mast mounted thereon, and a plurality of supporting legs, serving to support said body upon a building, said supporting legs extending laterally from the body in mutually diverging directions and being provided, at their outer ends, with supporting feet by which they may rest upon said building, each supporting leg comprising a lower arm, which, at its inner end, is connected to a lower portion of the body, and an upper arm, which, at its inner end, is connected to an upper portion of the body, said two arms of each supporting leg extending in mutually converging directions towards the outer end of the supporting leg, where they are connected to each other.
A mast base of said kind is previously known through SE-C2511726. This known mast base is intended to be placed freely resting upon the roof of a building. In order to hold the base firmly resting upon the roof and prevent the base from being tilted when exposed to tilting moments caused by high wind loads, a ballast of high weight must be placed on a special platform mounted at the lower end of the body and serving to support said ballast, or must heavy weights be placed upon each supporting foot. This fact results in that already the total weight of the base will give reason to high vertical forces on the roof at each supporting foot. However, high wind loads acting on a mast mounted on tire base and on antennas secured to the mast may
result in a substantial increase in the vertical load on the roof occurring at individual supporting feet. Therefore, in order to make it possible to place the known mast base upon a roof, the roof has to be dimen- sioπed so as to be capable of carrying very high local vertical loads. However, within many regions where it is desired to place antenna masts upon buildings, the roofs of the buildings do not have sufficient load carrying capacity to be able to carry such high loads, which means that it is not possible to utilize mast bases of the kind disclosed in SE-C2511 726 on said buildings.
Another disadvantage of the known mast base is that, in order to counteract any tendency to a rotation of the body of the mast base around a vertical axis caused by wind forces, a special and in practice unfavourable design of the upper arm of two supporting legs placed on opposite sides of the body is reqruied. The invention has for its purpose to provide an improved mast base of the kind initially specified which makes it possible to avoid the above-mentioned disadvantages.
The mast base, according to the invention proposed for said purpose, is primarily characterized in that the lower arms of the supporting legs are rigidly connected to the body and in that the supporting feet are adapted to be firmly anchored to structural elements of the body of the buildling.
The invention avoids the risk that the mast base may cause high local loads on the roof of a building upon which the base has been placed, The vertical forces caused by the mast base can instead be carried directly by strutural columns or walls forming part of the body of the building. Moreover, the body of the mast base will be fixed against any rotation thereof
by the lower arms of the supporting legs which are rigidly connected to said body.
Similar to the known mast base above described, the mast base according to the invention may comprise four supporting legs.
However, according to the invention, the mast base may suitably comprise only three supporting legs. According to a preferred embodiment of the invention, these three supporting legs may consist of two suppor- ting legs, placed in alignment with each other on opposite sides of the body, and a third supporting leg, extending from the body in a direction perpendicular to said two supporting legs. A specific advantage of this embodiment is that it makes it possible to mini- mize the space above the roof of a building occupied by the mast base.
In order to make is possible to place a mast base of a certain standard design upon different types of buildings, each supporting leg may have an individually adjustable length as seen in plan view. The individual length of each supporting leg may then suitably be adjustable in steps. In this case, the supporting feet may preferably be mounted continuously adjustable on the supporting legs for limited horizontal displacement thereof relativly to the supporting legs.
In order to permit an adjustment of the length of each supporting leg, each of the two arms of each supporting leg may comprise two elements which are mutually displaceable in a telescopic manner and lockable in different relative positions, in which case the upper arm of each supporting leg may be pivotally connected to the body at its inner end, while, at its outer end, it may be pivotally connected to the lower arm.
The invention also relates to a method for mounting the mast base upon a building. This method is primarily characterized by inserting anchor rods, serving to anchor the supporting feet firmly to structu- ral elements of the body of the building in bored holes in said elements, intended to receive said rods, and fixing the anchor rods in said holes by injecting a hardenable material in the spaces between said rods and the walls of said holes, and by securing the suppor- ting feet to the anchor rods after the hardening of said material.
Below, the invention is further described with reference to the accompanying drawings, in which:-
Figure 1 shows a perspective view of a mast base according to an embodiment of the invention, selected by way of example only,
Figures 2 and 3 show plan views on a reduced scale of the mast base according to Figure 1, illustrating all supporting legs of the mast base in positions corres- ponding to the largest possible and shortest possible length thereof, respectively,
Figure 4 shows a side elevation of the mast base according to Figure 1, illustrating two supporting legs, which are located in alignment and opposite to each other, in positions in which one of said legs has its maximum length, while the other leg has its minimum length,
Figure 5 shows a partial view on an enlarged scale,, illustrating the connection between an outer portion of a supporting leg of the mast base and an associated supporting foot,
Figure 6 shows a corresponding partial view, illustrating the connection between an inner portion of the upper arm of a supporting leg and the body of the mast base, and
Figure 7 shows a cross-sectional view, illustrating the anchoring of a supporting foot to a structural column of a building.
The mast base shown in the drawings comprises a rigid body, generally designated 10 and formed as a vertically orientated framework having a generally square cross-sectional shape and comprising four upright supporting elements 11, located each at one corner of the framework and connected to each other by means of upper cross beams 12 and lower cross beams 13 and horizontal stiffening members 14 and inclined stiffening members 15 located between said cross beams.
Body 10 is intended to be supported upon a building in a position elevated from a flat roof of the building by means of three supporting legs, generally designated 16, which extend in mutually diverging directions from body 10 and which, at their outer ends, are provided with supporting feet 17 by which the supporting legs can be carried resting on structural elements of the body of the building with the supporting feet firmly anchored to said elements. -
Each supporting leg 16 comprises an upper arm 18, which at its inner end is connected to an upper portion of body 10, and a lower arm 19, which at its inner end is connected to a lower portion of body 10. These two arms 18 and 19 of each supporting leg 16 extend in mutually converging directions towards the outer end of the supporting leg, where they are connected to each other. At their inner ends, the lower arms 19 of the supporting legs 16 are ridigly connected to body 10 in order to be able to hold the body firmly fixed against any rotation thereof around its vertical longitudinal axis. In order to faciliate an individual ad- justment of the length of each supporting leg 16, the
upper arm 18 of each supporting leg is composed of two elements 18A and 18B which are mutually displaceable in a telescopic manner and lockable in different relative positions, while the lower arm 19 is composed of two elements 19A and 19B which are telescopically displaceable and lockable in different relative positions. Furthermore, at its inner end, the upper arm 18 of each supporting leg 16 is pivotally connected to body 10 by means of a pivot pin formed by a bolt 20, while, at its outer end, it is pivotally connected to the lower arm 19 by means of a pivot pin formed by a bolt 21.
In the illustrated embodiment, each one of the two elements 18A and 19A consists of an I-beam, while each element 18B and 19B; respectively, consists of two U-beams located on opposite sides of the web of the I- beam and having their webs facing the web of the I-beam. In order to make it possible to adjust the length of each of the two arms 18 and 19 in steps, elements 18B and 19B are provided with a plurality of through holes 22 and 23, respectively, which are evenly distributed along the length of said elements and can cooperate with through holes 24 and 25, respectively, provided in the outer portions of elements 18A and 19A, in order to make it possible to lock elements 18A and 18B, and 19A and 19B, respectively, to each other in desired positions by means of clamping bolts 26 and 27, respectively.
Each supporting foot 17 consists of a flat bottom plate 28 and two spaced-apart vertical supporting flanges 29 which are rigidly connected to the bottom plate and to which connecting members 30, provided at the outer ends of elements 19B of lower arms 19 of the supporting legs are connected by clamping bolts 31. In order to facilitate a continuous fine-adjustment of the positions of the supporting feet 17 relatively to the supporting legs 16, flanges 29 are provided with oblong
through holes 32 for bolts 31 which permit a limited displacement of bolts 31 in a horizontal direction.
Figure 7 illustrates how a supporting foot 17 can be mounted on a structural element of a building in a state in which it is firmly anchored to said element. Reference numeral 33 designates a supporting column of the body of the building and reference numeral 34 designates two roof plates resting upon said column. Before mounting mast base 10 upon the building, a ver- tical hole 35 is bored in column 33. In this hole, there is inserted an anchor rod 36 which is fixed in the hole by injecting a hardening material 37 in the space between rod 36 and the wall of hole 35. Hereupon, supporting foot 17, which in its bottom plate 28 is provided with a through bore 38 for an upper threaded portion of bar 36, may be fixed by means of a nut 39, mounted on said portion, in a state in which it rests upon column 30 via a distance piece 40 and the two roof plates 34 and is firmly anchored to the column. In the embodiment shown in the drawings, the mast base comprises three supporting legs 16, two of which are located in alignment with each other on opposite sides of body 10, while the third supporting leg extends from the body in a direction perpendicular to the two firstmentioned supporting legs. However, the invention is not restricted to said embodiment. Instead, many other embodiments are feasible within the scope of the invention as defined in the following claims. Only by way of example, it could be mentioned that the number of supporting legs as well as the orientation of the legs may be selected in another way. Furthermore, the detailed design of the body and the supporting legs may be varied in many different ways within the scope of the invention.