DE20301673U1 - Damping ring for drill excavators or drill devices, has spring devices comprising piston cylinder devices provided between ring flanges - Google Patents

Abstract

At least one spring damping device (1) is provided between the upper and lower mounting flanges used to form the ring. The volume of the piston rod (4) entering the cylinder (2) will compress the medium (6) inside the cylinder to such a degree that a desired static spring cushioning is obtained.

Description

Eckhard Petersmann ·..· '·'"·..·.:*.*&idigr;_##&iacgr;&Agr;&pgr;&igr; Jiange 2a

Hagen, February 1st, 2003 " ⁵⁸ * ^{1#19 Ha} S ^en

⁶ Phone: 02334 - 5 58 64

Petersmann@pit-germany.de

Description:

In the case of drilling excavators and/or drilling rigs which sink holes to a depth of up to 60.00 m and a diameter of up to 2.00 m, the drilling rods generally consist of so-called Kelly rods in various designs which extend and retract in a telescopic manner and on whose inner rods the drilling heads are located.

In the Kelly bar type described, the inner bar hangs on the rope and lifts the outer bars telescopically as it is lifted out until all the individual bars are lying on top of each other and the drill head can be lifted out of the bore.
The Kelly bar is frequently pulled out during the drilling process to empty the drill head.

It happens again and again that due to dirt etc. the outer drill rod is lifted and then falls down in free fall from an undetermined height.

The impact or the released impact energy passes unhindered into the gear head that surrounds and drives the Kelly bar and causes - in some cases irreparable - damage, the repair of which is extremely expensive and time-consuming.

In order to absorb this impact and dampen the impact energy and thus minimize subsequent damage, a device with springs and dampers is placed between the gear head and the support ring of the outer Kelly bar.

Due to the limited dimensions allowed by the design of the gears and the Kelly bars, generally only very small helical compression springs can be used.

As a result, quite a lot of springs have to be used. But even if the entire pitch circle, which in the described design has a diameter of 555 mm, is equipped with a maximum of springs (12 pieces), dampers (3 pieces) and anti-twist devices (3 pieces) or with 15 springs and 3 anti-twist devices, springs of this size are in no way capable of absorbing the falling energy of a free-falling, outer Kelly bar weighing 2,100 kg from a height of more than approx. 0.35 m. After all, this is an energy of 8,858 Nm.

In the case described, tests have shown that 15 cylindrical screw compression springs with the dimensions Dm = 50 mm, spring wire = 10 mm, Io = 173 mm, 10 windings, spring rate R = 160 N/mm, spring travel 80 mm, break through after a free fall of the Kelly bar with a weight of 2,100 kg from a height of 0.266 m.

Any additional energy from a free fall from a greater height goes unbraked into the gear head. If the free fall is only 0.10 m higher, for example with the damping ring described, an additional 14g hits the gear head unbraked.

Due to the lifting speed of the Kelly bar of 1.00 m/s and the resulting extremely limited reaction time of the excavator operator, frequent impacts of this kind cannot be avoided.

The psychological strain on the excavator operator due to the constant, utmost attention required when pulling out the Kelly bar should not be underestimated.

Mr. Petersmann has developed a damping ring (A) whose dimensions are compatible with the existing damping ring described, but whose 6 (!!) spring dampers (1) are able to absorb the energy of a free-falling Kelly outer bar weighing 1,700 kg from a height of 4.04 m.

Tests on the object have also shown that such a damping ring (A) with 6 spring dampers

(1) absorbs the impact energy generated by a locked Kelly bar weighing 7,800 kg from a free fall height of 0.88 m (73,536 Nm)
This enormous spring damping behavior is generated by the use of spring dampers (1), which work on the basis of a compressible medium (6) and in which the spring and damping work is performed in one unit.

These spring dampers (1) do not require one of the usual helical compression springs or an additional oil damper.

Eckhard Petersmann Page S* for the Announcement -

O A piston rod (3) with a certain diameter and a turned piston plate (4) with

a diameter that is also determined is guided through a piston bearing (5) into a cylinder (2) filled with a compressible medium (6). The medium (6) is brought to a predetermined pressure at the factory. This pressure acts from the inside on the piston rod surface (3) and thereby generates a very specific force that tries to push the piston rod (3) out of the cylinder (2).

The piston plate (4) rests under the piston bearing (5) and prevents further expansion of the medium (6). In this state, the element resembles a pre-tensioned helical compression spring.

When a load impacts, the piston rod (3) and therefore also the piston plate (4) are moved into the cylinder (2).

In this case, the existing compressible medium (6) is inevitably compressed by the retracting piston rod volume (3), since this medium (6) is clamped in the cylinder (2) and cannot escape.

Due to the compressibility of the medium (6), the pressure in the cylinder (2) increases by a previously calculated value, continues to act on the piston rod surface (3) and thereby generates a counterforce which counteracts the impact force.

The highest pressure and thus the highest counterforce is achieved when the piston rod (3) has been completely retracted into the medium (6) of the cylinder (2).

The static spring rate R is generated by the ratio "piston rod volume, volume of the medium and the preload force of the medium".

Since the piston plate (4) is only slightly smaller in diameter than the inner diameter of the cylinder (2), it acts like a baffle plate when it is quickly inserted into the medium (6) and generates a high counterforce.

At the same time, the medium (6) must necessarily flow through throttle/bypass holes (8) in the piston plate (4) as well as through an annular gap (7) between the inner wall of the cylinder (2) and the piston plate (4). The frictional force losses generated in this way are added to the compression force, thus also counteracting the force that is applied and are dissipated as heat.
The highest energy absorption is achieved when the piston rod (3) is fully retracted and the piston movement is zero. The frictional energy is used up. Now only the compression pressure in the cylinder (2) acts on the piston rod surface (3) and resets the incoming load.
Since the piston plate (4) is again guided through the medium (6) and this medium (6) - just like during retraction - must inevitably flow again through the throttle/bypass bores (8) of the piston plate (4) and the annular gap (7), a corresponding return damping is also present when the piston rod (3) is returned.

All three forces, compression force of the medium, impact plate energy absorption and frictional force losses, together result in the absorption capacity of the spring damper and therefore determine - depending on the number - the absorption capacity of the damping ring (A)

?n, 01.02.2003

⁴ -> Petersmann

Claims (7)

1. Damping ring (A), consisting of an upper (B) and a lower (C) receiving flange of indeterminate size, characterized in that one or more spring dampers ( 1 ) are detachably located between these flanges, in which the volume of the retracting piston rod ( 3 ) compresses the volume of the medium ( 6 ) to such an extent that a desired static spring rate is achieved. 2. Damping ring (A), characterized in that in the spring dampers ( 1 ) located between the flanges (B + C), a loss of frictional force is generated by the technical design of the piston rod ( 3 ) or the piston plate ( 4 ) or the annular gap size ( 7 ) or the throttle/bypass bores ( 8 ) or the inner cylinder wall or all components together, which counteracts the force acting from the outside, is added to the static force, thereby generating a dynamic spring characteristic and thus absorbing the accumulating energy. 3. Damping ring (A), characterized in that by introducing a higher preload pressure and thus a higher initial force into the spring dampers ( 1 ), the absorption capacity of the spring dampers ( 1 ) can be increased without changing the dimensions of the spring dampers ( 1 ) or the damping ring (A). 4. Damping ring (A), characterized in that by introducing vertically movable anti-twisting devices (D) between the flanges (B + C), a rotation of the flanges (B + C) against each other in the horizontal direction is prevented. 5. Damping ring (A), characterized in that damping rings with very different force absorption can be produced by technical and/or constructive size changes on the flanges (B + C) and/or on the spring dampers ( 1 ) and the anti-twisting devices (D). 6. Damping ring (A), characterized in that the spring dampers ( 1 ) can be replaced individually in case of repair without dismantling the entire ring. 7. Damping ring (A), characterized in that the existing spring dampers ( 1 ) can also be used individually.