WO1999057411A1

WO1999057411A1 - Pneumatic submersible boring tool

Info

Publication number: WO1999057411A1
Application number: PCT/CZ1999/000011
Authority: WO
Inventors: Vladimír KOUDELKA; Jan S^¿TROS
Original assignee: Permon S.R.O.
Priority date: 1998-05-04
Filing date: 1999-05-04
Publication date: 1999-11-11
Also published as: DE69905245T2; EP1076754A1; AU3593999A; CZ136198A3; ATE232264T1; EP1076754B1; DE69905245D1

Abstract

A pneumatic submersible boring tool which is comprised of a front cover (4) with a working tool and with its arrestment, a rear input body (8) with a built in water valve and a working cylinder (1), wherein a striking piston (2) is guided that is provided with axial and side filling and exhaust ducts, whereby, said piston extends into a cavity (14) of said input body (8) by its rear extended part (21) with a filling recess (27) on its surface, which consists in that the front working compartment (17) of the working cylinder (1) is interconnected by a filling groove (16), provided on the surface of said striking piston (2), by a side filling duct (18) connected with it that passes through the wall of said striking piston (2), and by an axial filling duct (19) arranged in the rear extended part (21) of said striking piston (2), connected on said side filling duct (18), with a cavity (14) of said input body (8) whereby a closing pin (15) is built in axially in said cavity (14), and whereby the front face of said pin (15) is placed within the axial longitudinal section that is delimited by the front and the rear dead centres of said rear face (20) of said rear extended part (21) of said striking piston (2) and the external diameter of said closing pin (15) is smaller than the internal diameter of said axial filling duct (19). Pneumatic tool preferably consists of an axial exhaust duct (24) provided in the front part of said striking piston (2), wherein mouths said side exhaust duct (23) that passes through the wall of said striking piston (2) and is a continuation of said exhaust groove (22) formed on the surface of said striking piston (2) and also said side release duct (34) that passes through the wall of said striking piston (2) and is a continuation of the filling groove (16) provided on the surface of said striking piston (2) and interconnected with said bottom working compartment (17) of said working cylinder (1), whereby in said axial exhaust duct (24) an exhaust inertial slide valve (32) of pipe-like shape is placed so that it can slide.

Description

Pneumatic Submersible Boring Tool

Field of the Invention

The present invention relates to a pneumatic striking tool, preferably to a pneumatic submersible boring hammer.

Background of the Invention

Submersible boring hammers cannot increase their output characteristics by increasing their lateral dimensions, e.g. by increasing the working cylinder diameter, as the dimensions are delimited by the bore diameter and by the annular space necessary to exist between the bore wall and the external diameter of the hammer, whereby, this space is used to raise borings out of the bore by exhaust air.

But it is known to increase the installed output of submersible hammers not only by increasing the air pressure used, but also by a system of compressed air distribution and by the following arrangement of the filling and the exhaust ducts and recesses that supply compressed air into the working compartments of the cylinder and take away exhaust air.

The known and commonly used plate, ring, slide and flap distribution systems usually operate on the principle of an air pressure drop in the cylinder compartment which is being filled after opening of the exhaust duct. From the point of view of the installed output and efficiency it is disadvantageous that the moment of closing one working cylinder compartment at the same time is the moment of opening the filling of the opposite working compartment. This makes impossible to use a controlled air expansion in the cylinder compartment that is being filled without simultaneous backpressure growth in the opposite compartment. Moreover, the so arranged distribution systems are sensitive to the used lubricant, moisture and impurities in the supplied compressed air. They are intricate and, therefore, also cost intensive in production and they incline to be defective and unreliable in service.

A better solution is a system without any independent distribution system, where the compressed air distribution to the working compartments of the cylinder is controlled by the striking piston directly in relationship to its momentary position.

For example, the specification EP 40026 discloses a valveless boring tool having a cylinder and a piston that form the upper and the bottom working compartments together with the cylinder. The piston comprises an axially arranged filling opening, a separate axially arranged exhaust opening and filling and exhaust ducts formed at least partially in the wall of the working cylinder. Subject to the piston position in the cylinder in co-operation with the input pipe they provide for compressed air distribution into the working compartments and for output of exhausted air from the hammer. The input pipe axially passing across the upper working compartment can be fixed in an input body or it can be carried by a piston.

Specification US 5,318,140 discloses a submersible hammer that is comprised of a working cylinder and a piston mounted so that it can move in a cylinder. The input body of the hammer is provided with an extension that comprises a valve part, whereby, the valve part co-operates with the central opening of the piston. A lightening is made in the central opening of the piston that makes possible to interconnect the 3

compartments above and under the valve part in certain piston position.

Generally, the known solutions of this kind differ in detailed design of the filling and the exhaust ducts and the recesses in the piston, the cylinder and in other connected parts of the hammer and the boring bit. Usually, they make possible in one or in both working compartments of the cylinder to close the intensive filling of the respective working cylinder compartment and the subsequent air expansion in it before opening the exhaust independently of circumstances in the opposite cylinder compartment. From the point of view of the output installed and the efficiency, it remains as a disadvantage that the closure of the filling of the given working cylinder compartment in the given piston stroke position means opening of the filling of the same working compartment and, therefore, it brings about rising of back pressure in the same position of the opposite stroke. In the reverse stroke such relations are desirable, as the piston has to be halted in the back dead centre without an impact on the face of the rear working compartment. This can be utilised advantageously by intentionally making a compression compartment that is closed by piston in the rear dead centre, function of which is to act as an accumulator that makes possible to utilise a part of the energy passed on the piston during the reverse stroke for its acceleration in the initial phase of the striking stroke. However, in case of the striking stroke the backpressure produced by premature opening of the filling of the front cylinder working compartment causes undesirable piston breaking. Another disadvantage of this system is that for accelerating the piston it is not possible to utilise the whole length of the striking stroke because in its last phase before a blow, the exhaust duct is opened, what brings about a rapid drop of air pressure in the rear working 4

compartment of the cylinder. Together with the mentioned backpressure rise in the front working compartment in this phase of the piston movement the piston starts to be significantly braked with a consequent decrease in its striking speed and impact energy, i.e. a decrease of the installed output of the tool and of its total effectivity.

A disadvantage of the known designs is also the interconnection between the front working compartment and the cavity in the input body that is always at least partially formed in the wall of the working cylinder. Thereby, the cylinder is made thinner in the front part which is the most stressed one by abrasion caused by the bored off rock exhausted.

Summary of the Invention

The above mentioned disadvantages are eliminated by the embodiment of a pneumatic striking tool, in this case of a pneumatic submersible hammer according to the present invention, which is comprised of a front cover with a working tool and with its arrestment, a rear input body with a built in water valve and a working cylinder, wherein a striking piston is guided that is provided with axial and side filling and exhaust ducts, whereby, said piston extends into a cavity of said input body by its rear extended part with a filling recess on its surface.

Subject of the invention consists in that the front working compartment of the working cylinder is interconnected by a filling grove, provided on the surface of said striking piston, by a side filling duct connected with it that passes through the wall of said striking piston, and by an axial filling duct arranged in the rear extended part of said 5

striking piston, connected on said side filling duct, with a cavity of said input body whereby a closing pin is built in axially in said cavity, and whereby the front face of said pin is placed within the axial longitudinal section that is delimited by the front and the rear dead centres of said rear face of said rear extended part of said striking piston and the external diameter of said closing pin is smaller then the internal diameter of said axial filling duct.

According to one preferred embodiment of the present invention said closing pin is formed by a front part of a water valve body.

According to another preferred embodiment, in an axial exhaust duct, made in the front part of said striking piston, wherein apart from said side exhaust duct passing through said wall of said striking piston, also said side release duct is mouthed, which passes through said striking piston wall and which follows in said filling groove made on the surface of said striking piston and which is connected with said cylinder bottom working compartment, an exhaust inertial slide valve of pipe-like shape is placed so that it can slide and in said axial filling duct of said striking piston said filling inertial slide valve of pipe-like shape is placed so that it can slide.

It is also advantageous, when on the rear extended part of said striking piston is between said filling recess and said adjacent rear working face of said striking piston a cylindrical part is made which in said rear cylinder working compartment defines length of the compression compartment that is delimited by said input body front face, said adjacent internal diameter of said working cylinder, said striking 6

piston rear working face and by external surface of said cylindrical part of said striking piston rear extended part.

Another advantageous embodiment of the present invention is when said rear extended part of said striking piston is formed as a separate part mounted in the rear part of said striking piston and this separate part is made of a plastic.

By making a pneumatic striking tool according to this invention it is possible to fill the front and the rear cylinder working compartment during the selected sections of the striking and the reversing stroke at full input air pressure directly from the input body cavity, and each of both working cylinder compartments independently of each other, using short and substantially straight and sufficiently dimensioned sections without losses that would otherwise be caused by cross-sectional and directional changes in the compressed air flow route. Also independently of each other, it is possible, from the point of view of tool effectivity, to use in both cylinder working compartments the desired compressed air expansion in an interval between the closing of filling and the opening of exhaust. The full piston working stroke from the rear dead centre up to the blow moment is utilised during the striking stroke to accelerate the piston as a consequence of the exhaust and filling inertial valve and release duct activities, and this without the counter-pressure effect in the cylinder front working compartment, which would otherwise be formed by opening the filling of the front working compartment and by compression caused in it. The so, according to the invention, controlled cycle of filling and exhausting the cylinder working compartments, combined with reverse stroke energy accumulation in the compression compartment of the rear dead centre increases blow rate of the striking piston combined with a growth in its impact velocity 7

and consequently also of its impact energy, what indicates a growth in installed output of the striking tool and in its effectiveness. Creation of a rear extended part of said striking piston by using a separate part mounted in the rear part of said striking piston and the possibility to. make this separate part from plastic is practical considering the impact fatigue stress of said piston and inertial forces acting on the rear extended part of said striking piston. This embodiment simplifies production of said tool and increases its operational safety. For design and production simplicity it is preferable if the closing pin controlling, in cooperation with the mouth of said axial filling duct, opening and closing of filling the cylinder front working compartment is formed by the front extended part of the water valve body.

Industrial Use

Design according to the present invention can find use in case of all input air pressures that come into consideration. The design is compact, non-demanding in production and consequently also in price. The design is simple and consequently insensitive to operational conditions, staff and maintenance.

Brief Description of the Drawings

The attached drawing shows an example of an embodiment of a pneumatic striking tool, in this case of a submersible boring hammer, according to this invention, where Fig. 1 shows a section along its longitudinal axis and Fig. 2 shows a partial section through an alternative embodiment of the rear extended part of a striking piston and through the adjacent part of an immersible hammer. 8

Detailed Description of the Invention

Fig.l shows a striking piston 2_ deposited so that it can move in a working cylinder _1. A front cover _4 with an arresting ring _5, and a boring bit 6> with an exhaust pipe ^8 fixed in it, are fastened by means of a front thread 3_^ in the front part of the working cylinder 1_. By means of a rear thread 1_ an input body 8_^ is fixed in the rear part of the working cylinder 1_. A water valve body 9_ with a spring K) and a cone 1_1_ and a valve seat 12, are placed in the input body 8_. The valve body _9 is provided with openings 1_3 that interconnect the compartment adjacent to the cone 1_1_ with a cavity 1_4 of the input body 8_. The front part of the valve body 9_ is extended and forms a closing pin 15. A filling groove 1_6 is provided on the surface of the front part of the striking piston 2! that interconnects the front working compartment 1_7 of the working cylinder 1. with a side filling duct 1_8_ that passes through the wall of the striking piston _2 and is a continuation of an axial filling duct 1_9. This duct 1_9 passes through a rear face 2_0 of a rear extended part 2_1 of the striking piston 2_ and mouths into the cavity 1_4 of the input body _8_. The surface of said striking piston 2_ is also provided with an exhaust groove 2_2 that is interconnected by a side exhaust duct 2_3 that passes through the wall of the striking piston 2 , with an axial exhaust duct 2_4_ that passes through a striking face 2_5 of the striking piston _2 and is a continuation of a drilling 3_9 of a drilling bit 6 . The rear extended part 2_1 of the striking piston 2_ passes through an opening in the front face 2_6 of the input body _8_. A filling recess 2_7 is provided on the surface of the rear extended part 2JL, whereby said recess 2_7 is delimited by two cylindrical surfaces. The front cylindrical part 2_8_ of the rear extended part 2_1_ of the striking piston 2_, adjacent to the rear working face 2_9 of the striking piston 2_, determines the length of the compression compartment that is 9

formed during the reverse stroke of the striking piston 2_ in the rear working compartment 3 _ of the working cylinder _1. The internal wall of the cylinder _1 is provided with an exhaust recess 3JL that is adjacent to the rear working compartment 3 of the working cylinder .1. In an axial exhaust duct 2A_ an exhaust inertial slide valve Υλ_ is placed so that it can slide, whereby its front position is delimited by a front stop 33 and the rear one by the bottom of an axial exhaust duct 2 . A release duct _3_ i-^{s a}ls° mouthed into an axial exhaust duct 24, whereby said duct 3_i passes through the wall of the striking piston 2_ and it is interconnected by a filling groove 16 with the front working compartment 1/7 of the working cylinder 1 . A filling inertial slide valve 3_5_ is placed in the axial filling duct 1_9 so that it can slide, whereby its rear position is delimited by a rear stop 3_6_ and its front one by the bottom of the axial filling duct 19.

Fig. 2 shows an alternative embodiment of the striking piston 2 , where its rear extended part 2_1 is formed by an independent part _3_Z with a passing axial filling duct 19_, a filling recess 27, a rear face 2_0_ and a front cylindrical part 28_. The front part of the separate part 7_ forms the rear stop _3__. °f ^tne filling inertial slide valve 35.

A tool according to the present invention operates in the following way:

When compressed air is brought into the striking tool, the cone 1_1 opens flow of compressed air through the openings 1_3 of the valve body 9_^ into the cavity of the input body !3- From there, compressed air is led through the axial filling duct 19, the side filling duct 1_8 and the filling groove _1_6 into the front working compartment 1_7 of the working cylinder 1_. The striking piston 2_ is accelerated by the force of 10

compressed air in the front working compartment 1_7 towards the rear dead centre. From the rear working compartment 9_ exhaust air from the previous cycle of the piston 2_ escapes through the exhaust recess 3J1, the exhaust groove 2_2, the side exhaust duct 2_3' ^tne a^χial exhaust duct 2_4, the exhaust pipe 3_8 and the boring 3_9 of the bit _6 to the bottom of the bore and thereby to atmosphere. The striking piston 2 carries away with it the exhaust inertial slide valve 32_ and the filling inertial slide valve 3j__.' that are leaned against the respective stops as a consequence of action of inertial forces, so that they are held shifted into their front positions, i.e. flows through the side exhaust duct 2_3 and the side filling duct 18_ are open, flow through the release duct 34 is closed. At certain phase of the reversal stroke, the rear working face 29_ closes the exhaust recess 1 ^and thereby also all exhaust from the rear working compartment 3J2- ^Tne striking piston 2_ continues in reverse movement and at the moment when the axial filling duct 1_9 is closed by the closing pin 1_5, filling of the front working compartment 11_ by compressed air is terminated, and in the next phase of the striking piston 2_ reverse movement expansion takes place in it. In the next phase of the striking piston 2_ reverse movement, the filling recess 21_ interconnects the rear working compartment 3_0_ with the cavity 1_4 of the input body 8_ and the rear working compartment _3_P_ starts to be filled with compressed air that, in relation to the pressure circumstances in the front _17_ and the rear 29_ working cylinder 1_ compartments, gradually slows down movement of the striking piston 2_ . In the next movement phase of the striking piston 2_, the striking face 2_5 opens flow into the exhaust pipe 38 , through which the exhaust air from the bottom working compartment 1_7 escapes to atmosphere through the boring 3_9_ of the bit _6. After closing of the filling recess 21_ by the front face 2_6 of the input body 8_, air in the rear working 11

compartment _3__2 i^s compressed, what, together with a pressure drop in the front working compartment 1/7, causes a rapid breaking of the striking piston 2 ^UP to ^a h lt in the rear dead centre. The exhaust 32_ and the filling 5_. inertial slide valves continue in their movements because of inertia and so they shift themselves into their rear positions delimited by their rear stops. Thereby, closing of the side filling duct 1_8_ and the side exhaust duct 22 ^ancl opening of the release duct 34 take place. By compression the striking piston 2 i^s accelerated forward towards the striking stroke, together with both inertial slide valves 2_. and 3_5_ that are held by inertia in their rear positions. In the next phase of the striking stroke, the filling recess 2 _ opens entry of compressed air from the cavity 1_4 of the input body Q_ into the rear working compartment 3JD. Then, the striking piston 2_ closes the exhaust from the front working compartment 1/7_. by its striking face 25. Compression that would otherwise rise in the front working compartment 1/7 is released through the filling grove 1_6, the release duct 21' the axial exhaust duct 2_4 and the boring 2 of the bit 6_ to atmosphere during the whole remaining part of the striking stroke of the piston 2_L. The striking piston 2_ continues in its striking stroke up to a position when the compressed air input into the rear working place 22_. through the filling recess 21_ is closed. In the next phase of the forward movement of the striking piston expansion in the rear working compartment 2P_ takes place and during further movement of the striking piston 2_, the closing pin _15_ opens input of compressed air into the axial filling duct 1_9 at certain moment, but air flow into the front working compartment 17_ through the side filling duct 1J3 and the side filling groove 1_6 is closed by the filling inertial slide valve 22• Before a blow of the piston 2_ on the bit _6 the exhaust recess 21 i^s opened by the rear working face 23_ of the striking piston 2_, but an exhaust from the rear working 12

compartment 2_. through the exhaust groove ?_ ^{anc tn}e side exhaust duct 3 does not take place, as the side exhaust duct 23 is closed by exhaust inertial slide valve 2_r_.. The striking piston i^{s a}ccelerated by expanding air in the rear working compartment 2_. ^UP to the moment of a blow, without any back pressure in the front working compartment 1/7. Not sooner than when the piston 2_ strikes on the boring bit j, the inertial slide valves 22 ^and 3 slide into their front positions by inertia. Thereby, the side filling duct 13 is opened by the filling inertial slide valve 3b_ and compressed air is brought to the front working compartment 1/7 through the filling duct 18 and the filling groove 1_6. Simultaneously, by opening the side exhaust duct 22 by the exhaust inertial slide valve 3_2 exhaust from the rear working compartment 2_... through the recess 21' the exhaust groove 2_2, the side exhaust duct 23, the axial exhaust duct 2Λ_ and the boring 22 °f the bit 6 to atmosphere is made possible. After a blow, the striking piston is accelerated into the reverse movement and its working cycle is repeated. By a controlled filling and releasing of the working compartments 3/7 and 2P_ according to this invention the output characteristics and effectiveness of this tool can be increased, whereby its design simplicity and undemanding production and operation are maintained.

Claims

13Claims

1. A pneumatic submersible boring tool which is comprised of a front cover with a working tool and with its arrestment, a rear input body with a built in water valve and a working cylinder, wherein a striking piston is guided that is provided with axial and side filling and exhaust ducts, whereby, said piston extends into a cavity of said input body by its rear extended part with a filling recess on its surface, characterised in that the front working compartment (17) of the working cylinder (1) is interconnected by a filling grove (16), provided on the surface of said striking piston (2), by a side filling duct (18) connected with it that passes through the wall of said striking piston (2), and by an axial filling duct (19) arranged in the rear extended part (21) of said striking piston (2), connected on said side filling duct (18), with a cavity (14) of said input body (8) whereby a closing pin (15) is built in axially in said cavity (14), and whereby the front face of said pin (15) is placed within the axial longitudinal section that is delimited by the front and the rear dead centres of said rear face (20) of said rear extended part (21) of said striking piston (2) and the external diameter of said closing pin (15) is smaller then the internal diameter of said axial filling duct (19) .

2. Pneumatic tool according to claim 1, characterised in that said closing pin (15) is formed by the front part of a water valve body (9) .

3. Pneumatic tool according to claim 1, characterised in that it has an axial exhaust duct (24) provided in the front part of said striking piston (2), wherein mouths said side exhaust duct (23) that passes through the wall of said 14

striking piston (2) and is a continuation of said exhaust groove (22) formed on the surface of said striking piston (2) and also said side release duct (34) that passes through the wall of said striking piston (2) and is a continuation of the filling groove (16) provided on the surface of said striking piston (2) and interconnected with said bottom working compartment (17) of said working cylinder (1), whereby in said axial exhaust duct (24) an exhaust inertial slide valve (32) of pipe-like shape is placed so that it can slide.

4. Pneumatic tool according to claim 1, characterised in that in said axial filling duct (19) of said striking piston (2) said filling inertial slide valve (35) of pipelike design is placed so that it can slide.

5. Pneumatic tool according to claim 1, characterised in that on the rear extended part (2) of the striking piston (2) between said filling recess (27) and said adjacent rear working face (29) of said striking piston (2) a cylindrical part (28) is made that in said rear working compartment (30) of said cylinder (1) defines the length of the compression compartment which is delimited by front face (26) of said input body (8), by the adjacent internal diameter of said working cylinder (1) , by the rear working face (29) of the striking piston (2) and by the external surface of said cylindrical part (28) of the rear extended part (21) of said striking piston (2) .

6. Pneumatic tool according to claim 1, characterised in that said rear extended part (21) of said striking piston

(2) is formed of an independent part (37) which is fastened to the rear part of said striking piston (2) . 15

7. Pneumatic tool according to claims 1 and 6, characterised in that said independent part (37) is made of plastic.