US 3482786 A
Description (OCR text may contain errors)
2 Dec. 9, 1969 G. v. HQGG 3,482,786
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17 26 27 I 13 74 W77 I 5! 2 United States Patent 3,482,786 APPARATUS FOR COMMINUTING MATERIALS Gerald V. Hogg, 27 Bronwydd Ave., Cyncoed, Cardiff, Wales Filed Nov. 10, 1966, Ser. No. 593,353 Claims priority, application Great Britain, Nov. 12, 1965,
6 Int. Cl. B02c 11/00, 19/06; B07b 3/00 U.S. Cl. 241-52 5 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a method of, and apparatus for, comminuting materials, and more particularly for pulverising particles of metal or other material to produce powder of a grain size suitable for use in powder metallurgy processes. The invention is more particularly concerned with pulverising scrap iron, mild steel or low alloy steels.
According to the present invention there is provided a method of pulverising metal particles which comprises the steps of entraining particles of metal or other material in a stream of compressed air or other gas, accelerating the particles to high speed and directing them against a target whereby a proportion thereof is caused to shatter into powder, separting the oversize particles from the powder, charging the oversize particles alternately into one or other of two supply containers, and discharging oversize particles from one of the supply containers into said compressed gas stream, whilst the other supply container is receiving a charge of said oversize particles.
The present invention also provides apparatus for pulverising particles of metal or other material which comprises a blast pipe connected to receive particles from a supply and to direct the particles in a high speed gas stream into a blast chamber in which they are shattered to form powder, a separator connected to receive a mixture of powder and oversize particles from the blast chamher and operable to separate out the oversize particles and return them to the supply, and wherein said supply comprises first and second supply containers operable alternatively to receive and store oversize particles from the separator, and to discharge the stored particles into the blast pipe, each supply container being operable in the one .sense whilst the other supply container is operating in the other sense.
The present invention further provides apparatus for pulverising particles of metal or other material which comprises a blast pipe for connection to a source of compressed gas and having an inlet for metal particles to be entrained in a stream of gas flowing through the blast pipe, a blast chamber into which the blast pipe is arranged to discharge, a target disposed within the blast chamber opposite the outlet of the blast pipe, a recycling conduit extending from the blast chamber, a separator connected to said recycling conduit to receive material carried from the blast chamber in the gas stream, to separate powder from oversize particles and direct the latter to an outlet, first and second supply containers connected to said outlet of the separator through first and second Patented Dec. 9, 1969 valves respectively, the first and second supply containers being connected to said inlet of the blast pipe via third and fourth valves respectively, whereby the supply containers can be opened alternately to the blast pipe and to the separator so that whilst one container is discharging particles into the blast pipe, the other supply container is receiving particles from the separator.
One form of apparatus in accordance with the invention will now be particularly described with reference to the accompanying drawing which shows a schematic view of the apparatus.
As shown in the drawing, the apparatus comprises a blast chamber 10' containing a blast shield or target 11, and a blast pipe 12 for discharging the material to be pulverised at high velocity into the blast chamber so that it will impinge against the blast target and be shattered into smaller particles. The target 11 and preferably also the internal walls of the blast chamber, should be made of a material which is highly resistant to wear, and will depend on the material being pulverised. For many purposes tungsten carbide or stainless steel will be suitable In order to achieve the high velocity discharge of the material, the blast pipe is connected to a source of high pressure air, or other gas, and the particles of material are introduced from a supply into the blast pipe through an inlet 13 in the wall of the ppie, and are carried along the pipe in the air stream. The inlet 13 is in the form of a stub pipe or Pitot tube having a downstream-facing outlet opening such that particles are sucked into the gas stream by the low pressure created on the downstream side of the outlet opening.
The outlet end of the blast pipe is provided with a supersonic venturi nozzle 14 to increase the velocity of the air and material flow and thereby accelerate the particles to supersonic speed. This venturi will also be made of a highly wear-resistant material.
The base of the blast chamber is connected through a T junction 15 to a recycling conduit 16 having a second inlet closed by a flap valve 17 to enable air to enter the conduit 16, after the compressed gas supply has been shut off, to clear material from the conduit. The conduit 16 leads to a first cyclone separator 18 which serves to separate out powder, and pass oversize particles into a recycling outlet 20 connected to the supply system. A second cyclone separator 21 connected from the first separator 18 via a pipe 19 is provided to separate dust from the particles of required size.
The supply system comprises downwardly-extending branched ducts 22, 23 connected from the recycling outlet of the first cyclone separtaor to the top of two supply containers 24, 25, each branch of the duct having a valve (V V respectively) for controlling the supply of recycled material to the supply containers. These containers must be sufiiciently strong to withstand the maximum blast pressure. The outlets of the two supply containers at the bottom of the containers are connected through downwardly-extending ducts 26, 27 to the common supply inlet 13 in the wall of the blast pipe. These two ducts are controlled by valves V V, respectively. In addition, control means 30 are provided for controlling the opening and closing of the various control valves, and also sensing means 31, 32 are provided in the containers for sensing the level of material in the containers and thereby operate the control means 30, Additional or alternative sensing means can be provided to sense the flow of material at various points in the system. These control and sensing means as well as the purpose of the valves will be discussed below.
In order to introduce an initial charge of material and subsequent fresh material into the supply system, a filling hopper 35 is provided which is connected to the top of one of the supply containers, for example contatiner 25, through a duct 36 controlled by a valve V In addition, or alternatively, a filling hopper may be provided to feed into the first cyclone separator.
Furthermore, in order to render the pressure in either container equal to, or above, the pressue in the blast pipe, each container is connected through a three way valve V with a separate source of compressed gas.
To consider now the operation of the machine, let it be assumed that valve V has been opened, to introduce an initial charge of material into container 25, and thereafter closed, the valves V and V are closed and valves V and V; are open. Upon discharging compressed air through the blast tube, the pressure in container 25 will quickly build up, (or can be increased by connection to the separate compressed gas source via valve V and permit material to flow through outlet valve V into the blast tube 12 where it will be entrained in the air flow and, after passing through the venturi nozzle, will shatter against the blast shield. The cominuted material will fall to the bottom of the blast chamber and will again be entrained in the air flow and carried through the blast chamber outlet and recycling conduit 16 into the first cyclone separator 18.
The oversize particles from the first cyclone separator will flow into the branched ducts 22, 23 and although some will build up against the closed inlet valve V the major part will flow through the open inlet valve V into container 24.
When the initial charge in container has passed into the blast pipe, the outlet valve V is closed, and thereafter invet valve V is opened to allow recycled material to flow into container 25. At the same time, inlet valve V of container 24 is closed and thereafter outlet valve V is opened and the recycled material in container 24 is fed to the blast pipe.
Thereafter the valves controlling the material flow into and out of the containers 24, 25 can be operated in a simple sequence to permit the containers to fill-up and discharge alternately. The control means can be arranged to operatet he valves automatically in a timed sequence or in dependence upon sensing means such as 31, 32 which are disposed within the bottom or outlet duct of each container to sense the termination of material flow from the container. In this way the system can be rendered fully automatic as well as continuous.
It will be appreciated that throughout the process described above the metal particles are maintained in the solid state.
1. Apparatus for pulverising particles of metal and other material comprising in combination,
a blast pipe having a first inlet for compressed gas, a
second inlet for material particles, and an outlet,
a high pressure gas source connected to said first inlet of the blast pipe to discharge a gas stream at high velocity therethrough,
a supply of material particles connected to said second inlet of the blast pipe to discharge particles'into the pipe for entrainment in said gas stream,
a blast chamber connected to said outlet of the blast a target, disposed within the blast chamber opposite said 4 blast pipe outlet, against which the material particles can impinge and shatter into powder,
a recycling conduit having an inlet connected to said blast chamber, and an outlet,
a vacuum generating particle separator located above the blast chamber connected to the recycling conduit outlet to receive powder and oversize particles 'fiowing in the gas stream from said blast chamber, and to separate the powder from the oversize particles the separator having a first outlet for oversize particles and a second outlet for powder,
first and second supply containers forming said material particles supply located beneath the particle separator, and each having a particle inlet in its top and a particle outlet in its bottom,
first and second supply ducts extending from said first outlet of the separator to the respective inlets of the first and second supply containers,
first and second inlet control valves disposed in said first and second ducts respectively to control the flow of particles from the separator to said containers,
third and fourth supply ducts extending from the first and second container outlets respectively to said second inlet of the blast pipe,
third and fourth outlet control valves disposed in said third and fourth ducts respectively to control the flow of particles from the containers to said blast P p valve control means operable to alternately open the inlet control valve and close the outlet control valve of one supply container while closing the inlet control valve and opening the outlet control valve of the other supply container,
the container with the outlet control valve opened being under positive pressure and the container having the outlet valve closed being under vacuum generated by the separator.
2. Apparatus according to claim 1 wherein said valve control means operates said vavles in a timed sequence.
3. Apparatus according to claim 1 having means for sensing the content of material of each supply container and for controlling the valve operating means in dependence upon the sensed content.
4. Apparatus according to claim 1 wherein each said supply container has an inlet for compressed gas whereby the pressure within the container can be raised at least as high as that in the blast pipe.
5. Apparatus according to claim 1 having a supersonic nozzle in said blast pipe for accelerating said particles to supersonic speed.
References Cited UNITED STATES PATENTS 2,103,453 12/ 1937 Graemiger 24l-40 2,560,807 7/1951 Lobo 24l80 XR 2,662,007 12/ 1953 Dickinson 24l39 XR 2,668,669 2/ 1954 Skelley 24l-39 2,891,734 6/1959 Andre-as 24l-52 XR HARRISON L. HINSON, Primary Examiner US. Cl. X.R. 24l -80, 40, 39