Cutting by use of rotating axially moving tool – Processes – Bit detachable
Patent
1995-10-30
1997-04-01
Howell, Daniel W.
Cutting by use of rotating axially moving tool
Processes
Bit detachable
137318, 408 56, 408 80, 408127, 408206, 408222, 408224, 470199, B23B 3500, B23B 4108, B23B 5100
Patent
active
056159811
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a method of forming a threaded hole, for example in a tank or tank lid, and to tools and rigs for forming such threaded holes. The invention further relates to a method of securing an internally-threaded collar in such a threaded hole.
Though various aspects of this invention may find applicability in diverse areas of industry, the invention is especially suitable for forming threaded holes in a tank, and particularly in an underground tank for containing a flammable and volatile liquid such as petrol. In view of this, the invention will hereinafter expressly be described with reference to underground petrol tanks, though it will be appreciated that the invention is not to be regarded as being limited thereto.
A common form of underground petrol tank comprises a steel (but sometimes reinforced plastic) vessel buried below ground level and having a neck upstanding from an upper part thereof, the neck having at its upper end an outwardly directed flange. The tank is closed by means of a lid which fits over the neck opening and is bolted to the flange in a liquid and gas-tight manner. Pipes for filling and drawing liquid from the tank, along with other services such as a level indicator, pass through the lid and are connected to appropriate pipe-work and so on within a chamber in the ground above the lid, which chamber is conventionally closed by a man-hole cover.
In one common arrangement for such a tank, the lid closing the neck is made of steel and has one or more circular openings therethrough, in each of which is welded a steel sleeve having upper and lower internal threads. The sleeves allow the connection of the required pipes to the tank, from above the lid, and of further pipes extending down into the tank.
Recent legislation and regulations based mainly on environmental grounds may require the provision of further services within an underground petrol tank. For example, in order to reduce the risk of overfilling a tank, certain authorities require an alarm system to be fitted to a tank, to give an alarm when the level within the tank rises above some predetermined level. In order to do this, and presuming there is no unused opening through the tank lid, a further opening must be formed in the tank lid, through which the required service may be fitted. Generally speaking, the further opening may be formed only by removing the tank lid, drilling and tapping the new opening and then replacing the tank lid.
In the case of a below-ground garage forecourt tank intended to hold petrol, the opening of the tank by removing the tank lid has to be performed with great caution and special measures have to be taken in order to avoid the risk of fire and explosion. Generally speaking, this may be performed only once appropriate notice has been given to the local government authority. The tank must be emptied of all petrol, and is then filled with water to displace all petrol fumes and vapours. The above-lid pipe-work and other services have to be disconnected from the lid, and then the ring of bolts around the lid may be removed. Once done, the lid may be lifted together with the fill-pipe and other equipment projecting downwardly from the lid. After the lid has been drilled and tapped, it is refitted to the tank and the tank then has to be subjected to a pressure test, in order to ensure that a perfect seal has been formed between the tank lid and the neck flange. Once tested, the pipe-work and services are re-made to the tank lid, and then the tank has to be completely drained of water, before it can be placed back in service. Moreover, the water will be contaminated and so has to be disposed of with considerable care.
It will be appreciated that the above procedures take a most considerable time and may be performed only by skilled personnel; a tank typically is out of service for one to three days if the lid has to be removed, for any reason. The effective cost to the garage proprietor is thus relatively high.
Though hole cutters including a threaded portion for tapping a cut hole ar
REFERENCES:
patent: 2369273 (1945-02-01), Bakewell
patent: 3293952 (1966-12-01), Fairbanks
patent: 3995655 (1976-12-01), Sands
patent: 4519415 (1985-05-01), Carn
patent: 4563924 (1986-01-01), Runkle et al.
LandOfFree
Forming threaded holes does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Forming threaded holes, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Forming threaded holes will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-534470