Boring or penetrating the earth – Boring without earth removal
Patent
1990-08-07
1991-10-15
Melius, Terry L.
Boring or penetrating the earth
Boring without earth removal
175297, 173 91, E21B 414
Patent
active
050566083
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a boring ram and in particular to a control mechanism for such a ram.
In United Kingdom Patent No 2111565 (assigned to British Telecommunications public limited company) a self propelled reversible boring ram is disclosed. Boring rams of this kind are now widely used for boring holes under footways and roadways to facilitate the provision of service ducts to carry telecommunication and power cables for example.
One problem associated with boring rams is that of providing a simple control mechanism to the device to effect reversing for example. Another problem is that of a piston in the ram reaching equilibrium.
It is one object of the present invention to provide a simple control mechanism for effecting switching of the direction of travel of a boring ram.
According to the present invention there is provided a boring ram of the kind comprising a tubular body which contains a reciprocal hammer and a pneumatically balanced control member for supplying working fluid to the hammer characterized in that the ram includes first and second working fluid inputs, the first working fluid input supplying working fluid to the hammer and the second working fluid input supplying working fluid to control means responsive to changes in fluid pressure to effect changes in the direction of travel of the ram, the control means having spring means which brings the control main to a first operating direction, working fluid pressure from the second fluid input acting a piston means of the control means to select operation in an opposed direction. Preferably the working fluid inputs are concentric and the two inputs may be connectable by way of a control valve to a common fluid pressure source. For the avoidance of doubt the term working fluid includes, but is not limited to compressed air.
A boring ram in accordance with the invention will not be described by way of example only with reference to the accompanying drawings of which:
FIG. 1 is a cross sectional view of the ram in forward working mode; and
FIG. 2 is a cross sectional view of the ram in reverse working mode.
Referring to the drawing, the boring ram which is of the kind sometimes called a self propelled percussion boring ram comprises a tubular body 1 which has a boring head 12 attached at one end, the boring head shown comprising a chisel point.
The tubular body 1 has an internal cavity containing a hammer 2 which has a main cylinder 14 connected by way of control ports 15 to the internal cavity. The cylinder 14 contains a control piston 3, the position of which determines whether the hammer 2 strikes at the forward end (FIG. 1) or at the rearward end (FIG. 2) of its reciprocations.
A shaft 16 extends from the rear of the control piston 3 and is slideably mounted between the walls of the internal cavity. The shaft 16 carries three servo pistons 5, 6 and 8, the purpose of which is hereinafter described and is biased by a coil spring 7 towards the reverse operating position. A full explanation of the working of the reciprocating hammer is given in UK Patent No 2111565 accordingly only abbreviated description is given herein.
In use in the forward mode referring specifically to FIG. 1, working fluid (e.g. compressed air) is supplied at equal pressure to coaxial inputs 9 and 10. A control valve 11, as shown may be used to commence the operation. Working fluid from the inlet 10 enters a tube 4 in the control piston shaft 16 causing the impacting piston 2 to oscillate, the piston 2 moving forward due to the air pressure until ports 15 are open at which point the pressure in the forward chamber rises. This pressure rise causes the piston to move towards the rear (after impaction) which once ports 15 clear the piston 3 allow the pressure to be released through the internal cavity to an exit port 17.
The air pressure also creates a rearward force on the control piston 3 which combines with the coil spring 7 to tend to switch the ram to the reverse operating mode. This force is counteracted by pressure from the fluid input 10 acting on the ser
REFERENCES:
patent: 3137483 (1964-06-01), Zinkiewicz
patent: 3642076 (1972-02-01), Coyne et al.
patent: 3759335 (1973-09-01), Coyne
patent: 4221157 (1980-09-01), Schmidt
patent: 4250972 (1981-02-01), Schmidt
patent: 4537265 (1985-08-01), Cox et al.
patent: 4596292 (1986-06-01), Crover
British Telecommunications public limited company
Melius Terry L.
LandOfFree
Boring ram does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Boring ram, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Boring ram will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-984109