US2802993A - Cylindrical clamp - Google Patents

Description

" Cami A. MATHERN ETAL 2,802,993

CYLINDRICAL CLAMP Filed July 14, 1954 Aug. 13, 1957 INVENTORS fir raga/H United States Patent CYLINDRICAL CLAMP Alfred Mathern and William Mathern, Maple Shade, N. J.

Application July 14, 1954, Serial No. 443,296

8 Claims. (Cl. 33397) The invention relates to clamps and particularly to clamps for fastening a cylindrical object to a concentric cylindrical support.

For certain U. H. F. transmitting antennas, a slotted cylindrical mast is used. Such a mast contains and supports a concentric coaxial transmission line for supplying the antenna with radio frequency (R. F.) energy. In assemblying and adjusting such an antenna, it is necessary at times that the mast and transmission line be longitudinally moved with relation to each other. If

the antenna is in place, such as on a high building or a tower, it is desirable that the mast and transmission line be firmly fastened to each other by clamps that allow easy lengthwise adjustment of the transmission line. Furthermore, it is desirable that the clamp act as a short circuit termination for another coaxial line formed by the antenna mast as the outer conductor and the transmission line as the inner conductor.

Accordingly, it is an object of the invention to provide a novel clamp for fastening a cylindrical .object to a concentric cylindrical support.

Another object of theinvention is to provide a clamp that fastens a transmission line within a cylindrical antenna and provides an electrical short circuit equivalent to a flat plate short circuit between the antenna and the transmission line.

Another object of the invention is to provide a clamp that rigidly fastens a transmission line within a cylindrical antenna and that permits the transmission line and the cylindrical antenna to be easily moved longitudinally with respect to each other.

Briefly, the clamp consists of a metallic cylindrical band for encircling the object to be fastened to the supporting element. The band may be fastened to the supporting element by any convenient means within the required limits of electrical performance, such as by radial brackets. A longitudinal slot runs the entire length of the band to allow the band to be tightened and released. A pair of semi-cylindrical and coextensive elements are fastened to the outer surface of the band at respective edges of the slot. These elements are spaced close to each other so that they form roughly an incomplete cylinder. The ends of the elements are externally and conically tapered, and a pair of caps having an internal taper that approximately conforms with the tapered ends is mounted on the ends of the semicylindricalelements. Means are provided for forcing the caps toward each other, and as this is done, the slot in the band is closed so that the band tightly encircles and clamps the object to be fastened. I

The invention is further explained in detail in the following specification, with reference to the accompanying drawing.

Figure 1 shows a plan view" of a'clamp in' accordance with the invention fastened to a surrounding supporting element;

Figure 2 shows a sectional view of the clamp taken along the line 22 in Figure 1;

Figure 3 shows another sectional view of the clamp taken along the line 3--3 in Figure 2;

Figure 4 shows an enlarged view of a portion of Figure 3 for explaining the operation of the clamp; and

Figure 5 shows an exploded perspective view of a portion of the clamp for explaining the construction of the clamp.

A plan view of a clamp constructed in accordance with the invention and in the released position is shown in Figure 1. The clamp comprises a metallic cylindrical band 10 in which a longitudinal slot 12 is cut thru the wall of the band 10 along its entire length. The band 10 is made of a hard yet resilient material, such as brass tubing, that is capable of being frequently tightened and released without losing its resiliency. A supporting element or structure 14, such as a slotted, cylindrical, U. H. F. antenna, surrounds the band 10. One such antenna, mentioned by way of example, is disclosed in U. S. Patent 2,658,143, granted November 3, 1953, to Fiet et a1. Three pairs of symmetrically spaced U- shaped brackets 16, of a material such as brass, for fastening the band 10 to the supporting structure 14 are welded to the band 10. While other means may be utilized to fasten the band 10 to the supporting structure 14, the brackets 16 represent a preferred embodiment.

The brackets 16 are securely held to the supporting structure 14 by threaded bolts 18 and nuts 20.

A sectional view of the clamp, takenalong the line 2-2 in Figure 1, is shown in Figure 2. Another sectional view of the clamp, taken along the line 3--3 in Figure 2, is shown in Figure 3. In Figure 3, two metallic semi-cylindrical elements 22 can be seen. These elements 22 are coextensive with each other, and are fastened to the outer surface of the band 10 at the respective edges of the slot 12. The elements 22 may be fastened to the band 10 by welding, brazing, or some other convenient method. When fastened to the band 10, the elements 22 form substantially a cylinder having a slot lying in the same radial plane as the slot 12 in the wall of the band 10. The two elements 22 may be mounted so that the slot 13 formed between the free edges of the. two elements 22 is the same width as, or is slightly wider or narrower than the slot 12 between the edges of the band 10. The width of this slot 13 enables the force applied on the object to be clamped to be controlled.

Figure 5 shows an exploded view of a portion of the clamp, including the semi-cylindrical elements 22, and the means for forcing these elements 22 together. 'It should be noted that the elements 22 would be fastened to the band 10. However, the band 10 is not shown in Figure 5 in the interest of clarity, so that the construction and operation of the clamp may be better under stood. The elements 22 are externally and conically tapered at their two ends 24. Two metallic caps 26,

30 having internal tapers 27, 31, respectively that con-' form substantially with the taper on the ends 24 of the elements 22, are mounted on the respective ends 24'oforiginally cylindrical in shape, both caps 26, 30 are cut. awayor recessed onone side, as shown in Figure 5, to

allow mounting them over the ends 24 of the elements 3 22 when fastened to the band 10. The recess or cut away portion is adapted to be positioned adjacent to the band and prevents the caps 26, from rotating after being mounted.

The cylindrical object to be clamped, for example, the outer conductor of a coaxial transmission line, is positioned within the band 10. Since the slot 12 does not allow a large amount of tightening of the band 10,,the outer diameter of the object to be clamped and the inner diameter of the band. It) when released should be very nearly the same, with the diameter of the band it) being slightly greater by virtue of the slot 12. When the edges of the slot 12 are forced together, the diameter of the band 10 is decreased so that the band 10 tightly and firmly encircles the object and clamps it uniformly around its outer periphery. When the edges of the slot 12 are allowed to separate, the resiliency of the band 10 causes the diameter of the band lit? to increase so that the band It) releasesthe clamped object. The brackets 16 should be sufficiently flexible or resilient to allow such movement of the band 10.

The edges of the slots 12, 13 are forced together by forcing the caps 26, 36 together. The caps 26, 30 may be forced together by a bolt which passes thru the opening 28 in one cap 26 and between the cylindrical elements 22 over the entire length thereof. One end 41 of the bolt 40 is threaded to conform with the threaded opening 32 of the other cap 34) and the other end of the bolt 40 has a head 4-2 which has a greater diameter than the opening 28 in the one cap 26. A metallic lockwasher 46 may be placed under the head 42 to prevent the bolt 40 from becoming loose after being tightened. The head 42 of the bolt 40 is provided with a hexagonal recess 43, shown in Figure 5, for rotating the bolt 40, such a bolt 40 being commonly known as an Allen-head bolt. A wrench having the same shape and size as the recess 43 may be used to rotate the bolt 40. As the bolt 40 is rotated in the proper direction, the threaded end 41 of the bolt 40 engages the threaded opening 32 of the cap 30 and forces the caps 26, 30 toward each other. As they are forced toward each other, the internal taper of the caps 26, 30, forcing against the externally tapered ends 24, forces the two elements 22 and the edges of the slots 12, 13 toward each other to tighten the band 10 around the object. When the band 10 is tightened, the tension on the band 10, and particularly ,in the region of the slot 12, fulfills the ideal condition of such a clamp, namely that the external force be applied along or tangent to the clamped surface. In Figure 4, an enlarged view of a portion of Figure 3 shows the elements 22 as they appear when the clamp is tightened. In the embodiment shown, the slot 13 between the free edges of the two elements 22 is narrower than the slot 12 between the edges of the band 10, hence the slot 13 between the free edges of the two elements 22 is shown closed. As the bolt 40 is rotated in the other direction, the caps 26, 30 are allowed to separate, and the resiliency of the band 10 causes the edges of the slots 12, 13 to separate and release the clamped object.

Because the clamp may be tightened and released by rotating the one bolt 40, it is particularly useful in locations which are difiicult to reach, such as within a cylindrical antenna. By using an L-shaped Allen-head Wrench extending thru a hole in the supporting element 14, the slots in a cylindrical antenna provide easy access for tightening and releasing the clamp, an operation quite difiicult otherwise. When the clamp is assembled and the bolt 40 threaded into the threaded cap 30, the threaded end 41 of the bolt 40 that projects beyond the threaded cap 30 may be enlarged or staked to prevent the cap 30 from falling off when the bolt 40 is rotated to release the clamp.

Typical dimensions of the clamp which are not limiting but are given by way of example only, are as follows:

Band 10:

Outside diameter 3 /2" Inside diameter 3% Length 3 /2" Slot 12 width Elements 22:

Outside diameter Inside diameter /8.

Length 2 /2" Length of taper Angle of taper 15.

Caps 26, 30:

Outside diameter /8" Inside diameter at start of taper /1,". Length /6" Length of taper Angle of taper 12. Opening 28, diameter 0.344". Opening 32 A -18 tap.

Bolt 40: Allen-head cap screw 7 -48 x 3 /2".

What is claimed is:

1. A clamp comprising a metallic band for encircling an object to be clamped, said band having a longitudinal slot running the entire length thereof, a pair of substantially semi-cylindrical and coextensive elements spaced close to each other and secured to the outer surface of said band at the respective edges of said slot, said elements having conically tapered ends, a pair of caps having tapers substantially conforming with said tapered ends and mounted on the respective ends of said elements, and means mounted on said caps for forcing said caps toward each other to force said semi-cylindrical elements together and tighten said clamp.

2. A clamp for fastening a cylindrical object to a supporting element comprising a metallic cylindrical band for encircling said object, said band having a longitudinal slot therethru running the entire length thereof, means for fastening said band to said supporting element, a pair of substantially semi-cylindrical and coextensive elements spaced close to each other so as to form an incomplete circle and fastened to the outer surface of said band at the respective edges of said slot, said elements having ends externally and conically tapered in a direction along the. length thereof, a pair of caps each having an. internal taper substantially conforming with said tapered ends mounted on the respective ends of said elements, and means positioned along the axis of said circle and linked to said caps for forcing said caps toward each other to force said semi-cylindrical elements together and fasten said clamp to said cylindrical object.

3. A clamp for fastening a cylindrical object to a supporting element comprising a metallic cylindrical band for encircling said object, said band having a longitudinal slot therethru running the entire length thereof, means for fastening said band to said supporting element, a pair of substantially semi-cylindrical and coextensive elements spaced close to each other so as to form an incomplete circle and fastened to the outer surface of said band at the respective edges of said slot to form an incomplete cylinder having a slot in the same radial plane as said longitudinal slot in said band, said elements having ends externally and conically tapered in a direction along the length thereof, a pair of caps each having an internal taper substantially conforming with said tapered ends and mounted on the respective ends of said elements, and means positioned along the axis of said circle and linked to said caps for forcing said caps toward each other to force said semi-cylindrical elements together and fasten said clamp to said cylindrical object.

4. A clamp for fastening a cylindrical object to a supporting element comprising a cylindrical band for encircling said object, said band having a longitudinal slot therethru running the entire length thereof, means for fastening said band to said supporting element, a pair of substantially semi-cylindrical and coextensive elements spaced close to each other and fastened to the outef surface of said band at the respective edges of said slot to form an incomplete cylinder, said elements having ends externally and conically tapered in a direction along the length thereof, first and second caps each having an internal taper substantially conforming with said tapered ends and mounted on the respective ends of said elements, said first cap having a central opening therein and said second cap having a central threaded opening therein, and a bolt having a head on one end thereof larger than said opening in said first cap for rotating said bolt and having threads on the other end thereof to fit said threaded opening, said bolt being positioned in the hollow space within said incomplete cylinder and in said openings with said head against said first cap and with said threads engaging said threaded opening for forcing said caps toward each other to force said semicylindrical elements together and fasten said clamp to said cylindrical object.

5. A clamp for fastening a cylindrical object to a hollow supporting element comprising a metallic cylindrical band for encircling said object, said band having a longitudinal slot therethru running the entire length thereof, means fastened to the outside of said band and symmetrically positioned therearound for fastening said band to said supporting element, a pair of substantially semi-cylindrical and coextensive elements spaced close to each other and secured to the outer surface of said band at the respective edges of said slot to form an incomplete cylinder having a slot in the same radial plane as said longitudinal slot in said band, said elements having ends externally and conically tapered in a direction along the length thereof, first and second caps each having an internal taper substantially conforming with said tapered ends and mounted on the respective ends of said elements, said first cap having a central opening therein and said second cap having a central threaded opening therein, and a bolt having a head on one end thereof larger than said opening in said first cap for rotating said bolt and having threads on the other end thereof to fit said threaded opening, said bolt being positioned in the hollow space within said incomplete cylinder and in said openings with said head against said first cap and with said threads engaging said threaded opening for forcing said caps toward each other to force said semi-cylindrical elements together and fasten said clamp to said cylindrical object.

6. A clamp for fastening a cylindrical transmission line longitudinally within a concentric cylindrical antenna comprising a metallic cylindrical band for encircling said transmission line, said band having a longitudinal slot therethru running the entire length thereof, a pair of substantially semi-cylindrical and coextensive elements spaced close to each other and secured to the outer surface of said band at the respective edges of said slot to form an incomplete cylinder having a slot in the same radial plane as said longitudinal slot in said band, said elements having ends externally and conically tapered in a direction along the length thereof, first and second caps each having an internal taper substantially conforming with said tapered ends and mounted on the respective ends of said elements, said first cap having a central opening therein and said second cap having a central threaded opening therein, a bolt having a head on one end thereof larger than said opening in said first cap for rotating said bolt and having threads on the other end thereof to fit said threaded opening, said bolt being positioned in said openings with said head against said first cap and with said threads engaging said threaded opening for forcing said caps toward each other to tighten said clamp around said transmission line, and brackets fastened to the outer surface of said band for fastening said clamp to said antenna.

7. A clamp as claimed in claim 6 wherein said brackets comprise a plurality of pairs of metallic brackets spaced symmetrically around said band in a plane and fastened to the outer surface of said band and the inner surface of said antenna for fastening said clamp to said antenna and providing an electrical short circuit therebetween.

8. A clamp comprising a cylindrical, metallic band for encircling an object to be clamped, said band having a longitudinal slot in a radial plane of said band that runs the entire length thereof, a plurality of fastening elements symmetrically secured to the outer surface of said band for fastening said band within a surrounding hollow cylindrical mast, a pair of substantially semi-cylindrical and coextensive elements spaced close to each other and secured to the outer surfaces of said band at the respective edges of said longitudinal slot, said semi-cylindrical elements having conically tapered ends and forming an incomplete cylinder having parallel slots diametrically disposed in the same radial plane as said longitudinal slot, said parallel slots extending the entire length of said semi-cylindrical elements and one of said slots registering with the longitudinal slot of said metallic band, a pair of caps having internal tapers substantially conforming with said tapered ends and mounted on the respective ends of said elements, and means positioned along the axis of said incomplete cylinder and linked to said caps for forcing said caps toward each other to force said semi-cylindrical elements together and tighten said clamp.

References Cited in the file of this patent UNITED STATES PATENTS 1,964,642 McCoy June 26, 1934- 2,203,806 Wolf June 11, 1940 2,205,474 Goeller June 25, 1940 2,474,062 Murphy June 21, 1949 2,531,519 Kumpf Nov. 28, 1950 2,603,347 Fish July 15, 1952 2,627,635 Seltzer Feb. 10, 1953 2,644,929 Kumpf July 7, 1953 2,684,221 Wollam July 20, 1954

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