RU2701277C1 - Screw batcher of powders of refractory metals - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to devices for supply of powders of refractory metals and can be used in various industries, where precision supply of powders is required. Screw feeder of powders of refractory metals consists of loading bunker of conical shape, housing of screw made in the form of hollow tube, and screw installed in it, and precision supply of powders into process zone is carried out through intermediate chamber located at an angle to screw housing and equipped with spiral conveyor. Spiral conveyor transmits rotation of small diameter screw, which serves as powder dispenser. Screw and helical conveyor rotation speeds are performed from different drives and synchronized. Inner surface of loading bunker, screw housing and spiral conveyor are made of hardened structural steel and subjected to electrochemical polishing.

EFFECT: task of present invention is development of screw dosing unit for powders of refractory metals for use in installations for precision welding of thin-sheet metals and production of parts with complex geometrical shape by electric arc in atmosphere of protective gases.

1 cl, 2 dwg

Description

The invention relates to devices for feeding powders of refractory metals and can be used in various industries where a precision supply of powders is required.

The use of helicoidal shells as transport devices has been known since the time of Archimedes and is widely used for moving powdered and bulk cargoes. The advantages and disadvantages of screw transport devices are discussed in detail in the works of various authors [A.O. Spivakovsky, V.K. Dyachkov // Transporting machines - M. Mechanical Engineering. - 1983]. Depending on the technological tasks associated with moving the load (for example, mixing), the screw of the screw conveyor devices can be continuous, tape, blade or shaped. The simplicity of the device, the tightness and small overall dimensions, made the screw conveyor devices indispensable in industrial applications. Despite a number of difficulties in the calculations and design of the auger feed of powders [V.A. Kerzhentsev, N.V. Perova // Scientific Bulletin of NSTU. - 2015. - T. 61 - No. 4 - P. 48-62], some problems (efficiency of the feed opening, powder compaction when moving others) can be avoided or minimized due to original design solutions. It is especially worth noting such parameters as high specific energy consumption, abrasion and shredding of the cargo, increased wear of the screw and the screw housing, and in the case of powder packing, the disadvantage of the device is the low metering accuracy and problems with ensuring stable operation, due to the complexity of the design of the dispenser. Thus, the development and design of screw powder dispensers is an urgent task.

A device for feeding bulk material from one apparatus to another in the presence of a pressure differential between the apparatus, consisting of a screw with a sealing chamber [M.S. Petrov, E.I. Golmshtok, R.M. Salikhov et al. // RF Patent No. 2392044 dated 06/20/2010] - analogue. To eliminate the bending moment at the end of the auger cantilever screw, as well as to switch the auger operation from the “to work out” mode to the “with layer” mode, the authors proposed that the last two or three turns of the auger be performed either two-way or with a gradual decrease in screw pitch to 0, 6-0.7 from the original. The disadvantage of the described device is that the bulk product by its nature is not a vacuum-dense medium, and its excessive sealing to seal the chamber leads to jamming of the screw. The practical implementation of this technical solution for dosing powders of refractory metals has led to rapid wear of individual elements of the device due to clogging of the screw batcher, clumping of the powder due to the formation of plugs and, as a result, jam the screw. The device is not suitable for the precision supply of refractory metal powders.

Known screw doser for bulk materials [Yu.A. Separate, A.V. Leaf fall // RF patent №132785 from 09/27/2013] - analogue. The authors with their technical solution sought to harmoniously combine in one device the efficiency of the loading hole, the lack of powder compaction during movement, the performance and energy efficiency of transporting bulk materials. The authors achieve accurate dosing of the powder by reducing the diameter of the discharge pipe. However, such an original solution as a cone screw and the presence of matching cutouts on a helical blade, the depth and quantity of which should vary depending on the nature of the transported material (its flowability, dispersion, etc.) leads to the fact that the implementation of such a dispenser as a universal device for industrial use is simply not possible. The main reason for the failure of the cone screw in operation is its jamming, since it is impossible to theoretically calculate and coordinate in practice for each bulk material the speed of rotation of the screw, the number and depth of cuts with different diameters of the screw at the loading hole and discharge port. Such a device is not suitable for accurate dosing of powders of refractory metals.

Known screw dispenser for bulk materials [K.I. Kolyshkin, B.S. Belitsky, B.V. Evseev et al. // RF Patent No. 103096 of 03/27/2011] - a prototype. The device is based on a screw batcher, additionally equipped with a pneumatic pulse device (agitator), mounted on the cover of the loading hopper. At the moment of short-term air discharge, the bulk product acquires the “pseudo-fluidity” property and freely “flows” into the inter-turn cavity of the screw, filling the voids between its blades. Next, the dosed product enters the outlet pipe on a locking plate fixed on the screw shaft and is poured into the packaging container through a receiving funnel through a centrifugal force. However, a detailed review of the stages of the prototype reveals a number of significant drawbacks, listed below. Product level control in the loading hopper is carried out by a material level sensor, while the product level is maintained constant. Thus, for the normal operation of the prototype requires an additional metering device that provides a constant level of the product, and in terms of its characteristics in terms of metering accuracy, an additional metering device should not be worse than the prototype, which significantly complicates the entire process chain. Another disadvantage of the prototype is the fact that in the intervals between pneumatic pulses, the inter-turn space of the screw is filled with the bulk product not as uniformly as under "pseudo-fluidity" conditions. In addition, the shock wave generated by the pneumatic pulse through the outlet pipe and the locking plate uncontrollably blows the bulk product into the packaging container. The dosing accuracy both at the moments of the pneumopulse, and in between, is grossly violated. Precision dosing of powders of refractory metals with such a device is impossible.

The objective of the present invention is to develop a screw batcher of powders of refractory metals for use in installations for precision welding of sheet metals and the manufacture of parts of complex geometric shapes by an electric arc in an atmosphere of protective gases.

The technical result is achieved due to the fact that the auger batcher of refractory metal powders consists of a conical shaped feed hopper, a screw housing made in the form of a hollow pipe, and a screw installed in it, and the powders are precision fed into the process zone through an intermediate receiver chamber, located at an angle to the auger body and equipped with a spiral conveyor, preparing powders and transmitting rotation of a small diameter screw, acting as a powder dispenser, and The rotational speeds of the screws and the spiral conveyor are carried out from different drives and synchronized, and the working surfaces of the screw batcher made of hardened structural steel were subjected to electrochemical polishing.

In FIG. 1 is a drawing of a screw batcher of refractory metal powders. The numbers indicate: (1) - a screw of small diameter; (2) - spiral conveyor; (3) - auger; (4) - auger housing; (5) - loading hopper; (6) - camera receiver; (7) - receiving funnel; (8) - cover.

In FIG. 2 shows a screw 3, a spiral conveyor 2 and a screw of small diameter 1.

The device operates as follows: refractory metal powder is poured into a loading hopper (5), which is closed by a lid (8); by rotating the screw (3), the powder is fed into the receiver chamber (6), where, using a spiral conveyor (2), the powder, undergoing additional tedding to eliminate clumping and uniform distribution, is fed into a small diameter screw (1), which, due to the small pitch of the screw and small diameter provides a controlled precision flow of powder through a receiving funnel (7) into the process zone.

Many materials, including powders of refractory metals, are prone to arch formation, with subsequent solidification on the walls of the hopper, the auger housing and other working surfaces of the dispenser. To prevent this, it is necessary that the material does not accumulate anywhere and is in constant motion. To facilitate the supply of powder to the screw and for low resistance to powder movement, the working surfaces of the dispenser were made of hardened structural steel followed by electrochemical polishing of the surface. The molybdenum hardness is 125 HB; tungsten hardness - 350 HB; hardness of hardened steel 40X - 552 HB [V.I. Anuryev / Reference designer-mechanical engineer // M. - Mechanical Engineering. - 2006.]. From the above data it follows that the working surfaces of the dispenser are not subject to abrasive wear by the powder of refractory metal and do not resist the movement of the powder. It is worth noting that the absence of a tedder in the loading hopper greatly simplifies the design of the dispenser.

Claims (1)

A screw metering device for refractory metal powders, comprising a conical shaped feed hopper, a screw housing made in the form of a hollow pipe, and a screw installed therein, characterized in that it is equipped with an intermediate chamber located at an angle to the aforementioned screw housing and equipped with a spiral conveyor transmitting rotation a small diameter screw, which serves as a batcher for the precision supply of powders into the process zone, while the first screw and spiral conveyor are connected to different drives with the possibility of syn chronization of their rotational speeds, and the working surfaces of the screw feeder are made of electrochemically polished hardened structural steel.

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