HAMMER ACTUATED BY MEANS OF A HYDRAULIC SYSTEM, IN PARTICULAR SUITABLE FOR USE IN DUSTY, CORROSIVE, AND SIMILARLY HOSTILE ENVIRONMENTS

Abstract: Hammer actuated by means of a hydraulic system, suitable for being used in dusty environments, in particular as the crust-breaker of aluminum electrolysis pots, comprising a device capable of generating an overpressure inside the bottom chamber (7) and of permanently causing a stream of filtered air to flow through the clearance (8) between the tool (6) and the sleeve (9), with said device being constituted by an intake duct (1), a filter (2), a non-return valve (3), a connection duct (10) and a non-return valve (11).

Description: The present invention relates to a hammer for producing holes, actuated by means of a hydraulic system, i.e., a hydraulic hammer, particularly suitable for use in dusty, corrosive environments, and similarly hostile environments. In such a hammers, as known, a "beating mass" sliding inside a cylinder and provided with a reciprocating motion, beats on a "sinker drill" or "working tool" and supplies it with the percussion motion it needs in order to produce the hole. Such a kind of hammers are used in the works inside mines and quarries, in roadworks, in industry, and so forth. The hydraulic-driven hammers are widely used, and are often preferred to the pneumatic-driven hammers thanks to their characteristics of higher compactness and of smaller overall dimensions than these latter. Unfortunately, they show the drawback, when are used in particularly dusty and/or corrosive environments, of requiring the use of complex protecting systems or devices, in order to be protected against the wear of the mechanical moving parts. These protecting systems or devices considerably limit the advantages deriving from the use of this type of hammers. In fact, it is known that the beating mass, by moving by reciprocating motion inside the sliding cylinder, behaves as a volumetric pump, causing an alternance of depressures inside the bottom chamber of the device, with the volume of said chamber being constituted by the surface-area of the cross-section of the beating mass multiplied by the stroke of it. Such depressures cause the intake of the dusts of material generated by the work of the tool, and anyway of the dusts existing in the surrounding environment owing to any causes, which dusts, often strongly abrasive, enter the tool guide bushing, causing a reduction in its useful life, and finally, by entering the bottom chamber, cause the abrasion of the beating mass too, which is rapidly worn. Such a drawback may often additionally cause, in said hydraulic-driven percussion devices, a pollution of the same hydraulic fluid, with negative consequences to the detriment of the whole hydraulic system, with burdensome and frequent servicing operations being rendered necessary. In order to obviate these drawbacks, for example a counter-pressure is generated by feeding compressed air or gases into the air gap between the tool guide bushing and the same tool, or into the room between the beating mass and the tool, which involves, as evident, the need far having available the necessary equipment for compressing and delivering said compresses gases, with the relevant problems arising of overall dimensions and costs. DE-A-3031464 (PELTO-HUIKKO) discloses a hydraulic striking machine according to the preamble of claim 1 comprising valve means for intermittently admitting air from the atmosphere to an impact compression space located between the piston and the tool to provide an intermittent current of puffing air by the action of the piston intermittently displacing air while striking the tool and channel means for leading the resulting puffing air current along the surface of the tool to clean the tool. The atmospheric air current penetrates to the impact space when the piston rises upwards after a stroke so creating a suction into the space. According to DE-A-3031464, said space is therefore alternatively under pressure and under suction, and the air current along the surface of the tool to clean the tool is provided only during the sinking stroke of the piston. Therefore, a purpose of the present invention is of providing a hammer actuated by means of a hydraulic system, which can be used in anyway dusty and corrosive environments without undergoing phenomena of abrasion and/or corrosion by the external agents, and which operates in a safe and reliable way even in such environments, with a minimum of servicing operations. Another purpose of the present invention is of providing a hammer actuated by means of a hydraulic system, particularly suitable for use in dusty and corrosive environments, which is simple and cheap to manufacture, and which does not involve the adoption of additional and/or auxiliary equipment of large overall dimensions, and of high cost. These and still other purposes and relevant advantages which will be clearer from the following disclosure, are achieved by a hammer actuated by means of a hydraulic system, particularly suitable for use in dusty and/or corrosive environments, which hammer, according to the present invention, comprises a device constituted by: at least one connection duct suitable for conveying, during the "rising" stroke of the beating mass of said hammer and owing to the effect of the same upwards movement of said beating mass, the filtered air contained inside said "top" chamber into the "bottom" chamber, constituted by the front face of said beating mass, by the cylinder inside which said beating mass slides, and by the rear face of the tool of said hammer, wherein on said connection duct there is installed at least one non-return valve suitable for enabling the filtered air to flow from said top chamber into said "bottom" chamber, and not vice-versa; said device being therefore suitable for generating inside said bottom chamber an overpressure both during said rising stroke and said sinking stroke, such as to permanently cause a filtered air stream to flow from said bottom chamber to the external environment through the clearance existing between the tool and the guide bushing for said tool. The present invention is disclosed in greater detail according to a preferred, non-exclusive form of practical embodiment thereof, made by referring to the hereto attached drawing tables, supplied for the purpose of merely illustrating the invention without limiting it, in which: Figure 1 shows a schematic longitudinal sectional view of a hydraulic hammer according to the present invention in its working step during which the beating mass is in its high position, and is beginning its downwards movement towards the tool; Figure 2 shows the same longitudinal sectional view as of Figure 1 in the working step of the hydraulic hammer in which the beating mass is in its low position and, after ending its sinking movement, and discharging its kinetic force onto the tool, is beginning its rising movement. In the figures the hydraulic system inside which the hydraulic fluid flows - however known from the prior art - is not shown. Referring to such figures, during the sinking stroke (Figure 1), during which the beating mass 5 moves downwards towards the tool 6, i.e., in the step during which said beating mass travels in the direction as shown by the arrow "A", and owing to the effect of its own movement, air is intaken from the external atmosphere through the intake duct 1 and, by flowing through the filter 2 and the non-return valve 3, fills the top chamber 4. During the sinking stroke, the valve 3 remains open and allows external, previously filtered, air to fill the top chamber 4, while the non-return valve 11 remains closed. During the rising stroke, during which said beating mass 5 moves upwards (Figure 2), i.e., in the step during which said beating mass moves in the direction as shown by the arrow "B", the valve 3 closes, the valve 11 opens, and the beating mass 5 compresses the filtered and clean air collected inside the top chamber 4 forcing it to flow, through the duct 10, into the bottom chamber 7, which, consequently, remains constantly under pressure. During the sinking stroke during which the beating mass moves downwards (according to the arrow "A"), the bottom chamber 7 results to be already filled with clean air which is compressed by the same sinking beating mass, and is forced to flow to the outside through the clearance 8 existing between the tool 6 and the bushing 9. Thus, the discharge of air towards the external atmosphere takes place through the clearance existing between the tool and the bushing, with said coupling being hence kept always clean. Thus, any air amounts from the surrounding atmosphere are prevented from entering through the air gap 8 during both of the rising stroke and the sinking stroke of the beating mass, with the entering being consequently prevented of abrasive dusts and/or of corrosive fumes, which would rapidly deteriorate the parts under mutual movement conditions, in particular the parts constituted by the bushing, the beating mass and/or the container cylinder. In particular, the present Applicant was able to see how the hydraulic hammer according to the present invention can be advantageously as a crust-breaker in the electrolysis pots for the production of aluminum metal, which, as well-known, are required to operate inside such environments, as the pot rooms, in which serious problems exist, which are caused by the presence of abrasive dusts (alumina, and the like), and by the corrosion by the fluorinated gases and fumes.

Claims: Hammer actuated by means of a hydraulic system, particularly suitable for use in dusty and/or corrosive environments comprising a device constituted by: at least one intake port or intake duct (1) suitable for conveying air, intaken from the external environment during the stroke of "sinking" of the beating mass (5) of said hammer and owing to the effect of the same downwards movement of said mass, into the "top chamber" (4), constituted by the rear face of said beating mass, by the inner surface of the cylinder inside which said beating mass (5) slides, and by the bottom of said cylinder, wherein on said intake duct (1) there are installed at least one filter (2), suitable for stopping the abrasive agents possibly contained in the intaken air, and at least one non-return valve (3) suitable for enabling the filtered air to enter said top chamber and not to leave it; characterized in that it further comprises at least one connection duct (10) suitable for conveying, during the "rising" stroke of the beating mass (5) of said hammer and owing to the effect of the same upwards movement of said mass, the filtered air contained inside said "top" chamber (4) into the "bottom" chamber (7), constituted by the front face of said beating mass, by the cylinder inside which said beating mass (5) slides, and by the rear face of the tool (6) of said hammer, wherein on said connection duct there is installed at least one non-return valve (11) suitable for enabling the filtered air to flow from said top chamber (4) into said "bottom" chamber (7), and not vice-versa; said device being therefore suitable for generating inside said bottom chamber (7) an overpressure both during said rising stroke and said sinking stroke, such as to permanently cause a filtered air stream to flow from said bottom chamber (7) to the external environment through the clearance (8) existing between the tool (6) and the guide bushing (9) for said tool. Hammer actuated by means of a hydraulic system according to claim 1, characterized in that it is used as a crust-breaker in the electrolytic pots for the production of aluminum metal.

Inventors: ZANNINI, GIANFRANCO
Applicants: TECHMO CAR S.P.A.
Application year: 1989
Main classification: B25D17
IPC codes: B25D17, C25C3, B23Q11