US3754683A

US3754683A - Apparatus for pneumatically placing semi-fluid materials

Info

Publication number: US3754683A
Application number: US00175764A
Authority: US
Inventors: J Broadfoot
Original assignee: Individual
Current assignee: Individual
Priority date: 1971-08-27
Filing date: 1971-08-27
Publication date: 1973-08-28
Anticipated expiration: 1990-08-28

Abstract

Quick-setting concrete is applied to a work surface by air conveying wet concrete through a hose to a nozzle and air conveying a dry accelerator powder for the wet concrete through a separate hose into juncture with the stream of suspended wet concrete a predetermined distance back of the nozzle. A positive metering concrete pump meters the concrete into a T-intersection where compressed air entering through one side of the top of the T impinges at substantially right angles to the flow of wet concrete through the base of the T resulting in shearing off of discrete pieces of wet concrete which are conveyed through a hose attached to the other side of the T-intersection. The positive metering concrete pump is directly attached to a positive metering device for the accelerator powder so as to maintain the ratio of wet concrete to accelerator constant.

Description

[ Aug. 28, 1973 1 APPARATUS FOR PNEUMATICALLY PLACING SEMI-FLUID MATERIALS [76] Inventor: John T. Broadfoot, 12714 Aurora Ave. North, Seattle, Wash. 98133 22 Filed: Aug. 27, 1971 211 App]. No.: 175,764

Related U.S. Application Data [63] Continuation of Ser. No. 175,764, June 18, 1970,

2,788,953 4/1957 Schneider 222/134 X 3,067,987 12/1962 Ballon et a1 222/145 X 3,176,878 4/1965 Hobgood et al. 222/134 3,385,476 5/1968 Young 222/134 Primary Examiner-Lloyd L. King Attorney-Seed, Berry & Dowrey [5 7] ABSTRACT Quick-setting concrete is applied to a work surface by air conveying wet concrete through a hose to a nozzle and air conveying a dry accelerator powder for the wet concrete through a separate hose into juncture with the stream of suspended wet concrete a predetermined distance back of the nozzle. A positive metering concrete pump meters the concrete into a T-intersection where compressed air entering through one side of the top of the T impinges at substantially right angles to the flow of wet concrete through the base of the T resulting in shearing off of discrete pieces of wet concrete which are conveyed through a hose attached to the other side of the T-intersection. The positive metering concrete pump is directly attached to a positive metering device for the accelerator powder so as to maintain the ratio of wet concrete to accelerator constant.

7 Claims, 4 Drawing Figures Patented Aug. 28, 1973 3,754,683

2 Sheets-Sheet 1 JOHN T. BROADFOOT INVENTQR.

BY @M ATTORNEYS Patented Aug. 28, 1973 2 Sheets-Sheet 2 m 8 7 Q. 3 35 43 44 /37 l (W HG=2 1 1F1IG== 3 JOHN T- BROA DFOOT INVENTOR.

BY I Q ATTORNEYS APPARATUS FOR PNEUMATICALLY PLACING SEMI-FLUID MATERIALS CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of Application Serial No. 175764, filed June 18, 1970, entitled APPA- RATUS AND METHOD FOR PNEUMATICALLY PLACING SEMI-FLUID MATERIALS, now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an apparatus and method for metering, conveying and applying wet concrete or other semi-fluid materials to a work surface, the semifluid material having a quick-setting additive or accelerator added thereto just prior to application to the work area.

2. Prior Art Relating to the Disclosure Quick-setting additives for concrete which provide an initial setting of the concrete in a matter of seconds have, of recent, become available. These additives have been added in dry form to a dry concrete mix which is then applied to a work area by means of a nozzle through which water in controlled amounts is directed. Such a process is very useful in providing ground support in mines and tunnels, thereby replacing the conventional timber and steel supports, and in repairing concrete structures, sewer lines, building retaining walls, water lines, etc.

Two basic methods of pneumatically placing concrete have been used, the dry method and the wet method. By the dry method, measured amounts of cement, sand and aggregate are mixed dry and forced by compressed air through a hose to a nozzle where water is introduced into the dry mixture before ejection from the nozzle. Theprincipal disadvantage of the dry method is the lack of adequate control of the amount of water added to the dry mixture. The amount of water used is critical to obtaining optimum concrete. The amount of water is controlled generally by the nozzle operator during application. His judgement, or the lack of it, is the criteria used and the results generally obtained are less than optimum. In addition to this disadvantage the dry process requires that the sand used be pre-dried, thus limiting use of the process to periods of good weather.

The so-called wet method utilizes a mixture of measured water and weighed amounts of cement, sand and aggregate. By adding a measured amount of water to the dry mix before application the quality and uniformity of the concrete can be closely controlled. Rebound, defined as the amount of material sloughing off the surfaceapplied during application, is reduced. One of the main problems encountered in the wet method is finding a way of transferring the wet concrete mixture from the mixing station through a'hose or other conduit to the nozzle. When applying concrete pneumatically it is desirable to use concrete mixes having a minimum of water (a stiff consistency) in order to promote quicker setting and reduced rebound. Such mixes are very difficult to convey through a hose because of their frictional resistance to passage through a hose. Machines for pneumatically placing wet concrete are known, such as the True Gun-All machine manufactured by the Detroit Tool Engineering Company of Lebanon, Missouri. This machine is incapable of smooth delivery of material and requires a high degree of maintenance. The amount of rebound is greatly affected by the flow of the material. When the flow of the material is uneven the rebound is significantly greater. Additionally, when a quick-setting additive or accelerator is added to the concrete mix before ejection from the nozzle using one of the True Gun-All machines it is impossible to get uniform distribution of the accelerator due to the erratic flow of wet concrete. The True Gun-All machines utilizes a cylindrical air pressurized mixing drum in which multiple paddle wheels rotate, each of the paddles having wiping blades thereon which contact the inner surface of the drum. Alternate slugs or measured amounts of wet concrete and compressed air from a source other than the interior of the tank are produced, the compressed air forcing the slugs of concrete through a hose to a nozzle.

Another means of conveying and spraying wet cementitious materials is disclosed in U.S. Pat. No. 3,212,759 which utilizes a pressurized tank holding the concrete, the tank having therein aereating means for uniformly dispersing high pressure air in the form of small bubbles within the mass of cementitious material to decrease its internal friction and facilitate delivery through a hose or a conduit.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of the overall apparatus of this invention which includes a positive metering fluid pump, a metering device for an accelerator powder for the pumped fluid, means connecting the fluid pump and the metering device directly together, and conduit means for deliveringthe mixed fluid and accelerator out of a common nozzle;

FIG. 2 is a cross-sectional view along section line 2-2 of FIG. 1;

FIG. 3 is a partial cross-sectional view along section line 3-3 of FIG. 2 illustrating the agitation means within the holding vessel for the accelerator; and

FIG. 4 is a cross'sectional view of the T-section into which the fluid is metered by the fluid pump and in which compressed air is impinged against the fluid at substantially right angles thereto.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, the overall apparatus of this invention comprises a frame or base support I on which is mounted a fluid pump 10, a supply hopper for the pump 20, and a metering means for an accelerator powder 30.

Fluid pumps capable of efficiently handling fluids of heavy consistency in which solids are entrained and which deliver a relatively smooth flow of the fluid are the type used in this invention. The pump is preferably of the type whereinthe fluid to be pumped is com-. pletely isolated from the moving parts of the pump. A preferred type of pump for the heavy fluids used in this invention, particularly concrete in which rock or aggregate up to one inch in diameter is included, is described in US. Pat. No. 3,180,272 which is hereby incorporated by reference. As described, fluid pumps of this type comprise a housing 11 comprised of a cylindrical shell with headers bolted thereto as closures for the open ends thereof. Each of the headers have a centrally located aperture to accommodate a rotary shaft. Air seals surround the shaft within the apparatus in the outer end walls. Entry and exit ports are provided in the cylindrical housing for a deformable or flexible hose to be received therethrough, the hose extending about and bearing against the interior surface of the cylindrical housing. One of the ports serves as the entry port for the material to be pumped with the other port serving as the exit port. Only the exit port 12 is shown in FIG. 1. Within the housing and mounted on the shaft is a power driven rotor means which squeezes the hose section within the cylindrical ring in repeating cycles starting at the entry end and working progressively towards the exit end. While the particular pump shown in the patent mentioned above utilizes two opposed elastic tires mounted for orbital travel around the center of the cylindrical housing, other rotor designs may be employed. If desired, only one elastic tire centrally mounted around the shaft may be used, or four elastic tires arranged at right angles to each other in pairs using the planetary arrangement shown in the patent may be used.

Pumps of the type shown in the above mentioned patent are capable of efficiently pumping heavy fluids containing aggregate ranging in size up to one inch in diameter. The shaft of the pump is connected to a suitable power means (not shown). In FIG. 1, a shield is shown shielding the belt driving the shaft of the concrete pump for safety reasons.

In front of the fluid pump and mounted on the same base support is a feed trough 20 in which cement and sand or cement, sand and aggregate are mixed prior to being pumped. The entry port of the pump communicates with the trough 20. The feed trough 20 includes several rotor blades 21 mounted on a shaft 22 running through the trough, the shaft being driven by suitable power means (not shown). The rotor blades 21 thoroughly mix predetermined amounts of wet concrete made up of water, sand and cement, or water, sand, ce ment and aggregate.

Directly connected to the fluid pump is a metering device 30 for metering predetermined amounts of a dry accelerator powder into the conduit for the wet concrete for quick setting thereof. The metering device comprises a cylindrical holding vessel 31 for the accelerator powder supported on a base support 32 by legs 33. The holding vessel has a bottom wall which tapers to an opening of smaller diameter than the cylindrical holding vessel. The opening in the bottom of the holding vessel communicates with an opening in the side wall of conduit 34 running horizontally to the vertically disposed holding vessel. Within conduit 34 is mounted a feed screw 35 rigidly attached to shaft 36 on which is mounted a variable speed pulley 37. Around the pulley is trained a belt 38 which is connected to the power means powering the fluid pump. A second pulley 39 around which belt 40 is trained, runs an agitator assembly to be described.'The agitator assembly is shown in cross-section in FIG. 2 and comprises a shaft 41 extending horizontally and transversely through the holding vessel 31. The shaft has two or more eccentric portions 42 on which are mounted section of chains 43 which, as shaft 40 is rotated, move vertically upwardly and downwardly to agitate the dry accelerator powder in the vessel. Also mounted on shaft 41 are one or more blades 44 which aid in maintaining the accelerator powder in a free flowing state. The holding vessel 31 is constructed so that it can be pressurized. The top of the holding vessel is fitted with a funnel 45 which aids in filling the vessel with the accelerator powder. The vessel is sealed with a domed closure 45 which seals around the top opening. The closure 46 is opened and closed by shaft 47. A small diameter valved conduit 48 communicating with the interior of the vessel 31 is provided to bleed off pressure in vessel 31 when refilling is necessary. The accelerator powder should be substantially free of moisture to achieve optimum results.

A conduit 50 is secured to the exit port of the concrete pump and extends to a T-section 51. The T- section 51 comprises a base portion 52 secrued to the discharge opening of the conduit 50 through which fluid is to be pumped and a top section 53 through one end of which compressed air is fed through conduit 54.

Semi-fluids of stiff consistency, such as a so-called dry concrete mixture, (one which has a minimum of water added thereto), are very difficult to pump any distance because of the high friction of resistance of the material against the internal walls of the hose or conduit through which they are pumped. It is a decided advantage of this invention that wet concrete of heavy consistency, that is wet concrete having a minimum of water therein, can be pumped distances greater than 200 feet without difficulty. This is accomplished by metering the wet concrete sections of the concrete with compressed air entering the top of the T-section through conduit 54. The compressed air impinges on the wet concrete being extruded into the T-section by the fluid pump and carries it through conduit 55 to nozzle from whic it is sprayed onto a work surface. The pressure of the compressed air needed to force the concrete through the conduit 55 can be regulated as desired. The discharge end of conduit 50 has an internal diameter about three inches as shown in FIG. 1 and the base of the T-section has an internal diameter of aboutthe same. The conduit 55 leading from the T-section of the nozzle shown in FIG. 1 has an internal diameter of about 2 inches. Though the diameter is reduced from 3 inches to 2 inches there has been no difficulty in conveying the concrete for distances over 200 feet and up to 300 feet. Compressed air at about 60 psi has been used although this can be varied as desired. Because the air stream is moving the concrete through the 2 inch line, the fluid pump becomes a metering machine having a maximum back pressure of about psi. The fluid pump delivers the wet concrete into the T-section in short sticks of material per rotor turn. The compressed air, however, exerts an elongating effect on the wet concrete resulting in a smooth metered feed at the nozzle.

The accelerator powder is introduced into the wet concrete through conduit 56 which intersects conduit 55 at an angle a predeterminted distance back of nozzle 60. The accelerator powder is fed into conduit 56 by feed screw'35 and is air suspended by compressed air coming through conduit 56 at substantially right angles to the feed of the accelerator powder. The air suspended accelerator powder mixes with the wet concrete coming through conduit 55 at the intersection of

conduits

55 and 56. The point of mixing of the accelerator and wet concrete depends upon the kind and amount of accelerator used, the consistency of the concrete and other factors. The distance may be from 3 to 10 feet back of the nozzle and preferably a distance of about 6 feet.

The amount of accelerator powder delivered into juncture with the wet concrete is directly and accurately controlled by directly connecting the metering device for the accelerator powder to the fluid pump. Preferably an amount of accelerator powder ranging from 2 to 8 percent by weight of the cement content of the concrete is used. The variable belt speed control connected to pulley 37 enables varying amounts of accelerator powder to be mixed with the wet concrete prior to expulsion of the concrete from the nozzle. The optimum amount of accelerator needed for a particular application can be ascertained by one skilled in the art. There are a number of accelerator powders for wet concrete commercially available and any of these may be used.

The overall system comprises a positive metering concrete pump to which is directly powered a positive metering dry accelerator feed. The concrete is conveyed by air through a hose and the powered accelerator is conveyed by air through a separate hose into juncture with the concrete hose a predetermined distance before issuing from the nozzle, preferably around 6 feet. The positive metering of the wet concrete into the air stream gives a very smooth feed at the nozzle and good distribution of the accelerator within the concrete mixture.

Utilizing the apparatus shown in FIG. 1, concrete containing aggregate up to one inch in diameter has been conveyed up to 200 feet with maintenance of good volume feed. A sand-cement mix has been conveyed over 300 feet. The concrete mixers which have been conveyed with the apparatus of this invention have consisted of about 40 percent rock or aggregate and 60 percent building sand, the aggregate having an average size of about 7/8 inch in diameter. Rebound is very much reduced with the apparatus of this invention over that accomplished by the prior art. Application rates are higher than machines of the prior art, ranging up to cubic yards per hour. The material is so quick setting that 12 inch knobs of material have been built up on vertical surfaces without sloughing. The concrete sets so quickly that even when water is flowing through an opening to be covered with concrete the hole can be covered without the water affecting it. For example, in a tunnel through which a full flow of water was flowing, a concrete mixture was sprayed. The concrete completely sealed off the opening through which the water was running without difficulty. The machine and method of this invention offer advantages over those known in the prior art in (1) higher production, (2) less dust, (3) less skill required by the operator of the nozzle as he does not have to control and observe rebound of the concrete being applied, (4) precontrol of water content of the concrete mixture, allowing optimum water content and minimum rebound, (5) no moisture control of the sand, (6) versatility of the apparatus (that is, it can be used for pressure grouting or for various other applications) and (7) easy maintenance and easy clean-up. No build-up of material in either the mixing equipment or the nozzle was noted during operation over fairly long periods of time. The pump and line are easily cleaned. The mixing equipment needs only to be washed out. No build-up in the last 6 feet of delivery hose was experienced in spite of the addition of accelerator to the wet concrete at a point 6 feet back of the nozzle. Another advantage of the machine of this invention is the ability to turn the accelerator on and off at will while applying the concrete. The accelerator powder used in most applications is expensive and it is highly desirable to be able to control the amount of accelerator used to minimize expense.

I claim:

1. Apparatus for spraying a continous stream of wet semi-fluid material capable of setting to a hard end product against a work surface comprising:

a spray nozzle,

a positive pump metering and pumping semi-fluid material to a discharge outlet thereof, means for suspending the semi-fluid material delivered to the discharge outlet in a gaseous medium and delivering it from the discharge outlet to the spray nozzle, said means including a conduit connected between the discharge outlet of the pump and the spray nozzle, and means impinging a compressed gas at an angle to the stream of semi-fluid material metered from the discharge outlet into the conduit at a pressure sufficient to shear discrete pieces of the semi-fluid material extruded into the gaseous stream by the pump and convey them in the suspended gas stream to the spray nozzle. 2. Apparatus for spraying a continuous stream of wet semi-fluid material capable of setting to a hard end product against a work surface comprising:

a spray nozzle, a rotary pump for metering the semi-fluid material to a discharge outlet, the rotary pump including a stationary ring, a compressible hose having circumferentially placed inlet and outlet ports therein extending about and bearing against the interior surface of the stationary ring, and a power driven rotor compressing the hose and producing a fluid pocket of material moving about the circumference of the ring progressively from the inlet port for extrusion of the semi-fluid material through the outlet port, and

means for suspending the semi-fluid material delivered to the discharge port by the pump in a gaseous medium and delivering it to the spray nonle, said means including a conduit connected between the discharge port of the pump and the spray nozzle, and means impinging a compressed gas at an angle to the stream of semi-fluid material extruded into the conduit by the pump at a pressure sufiicient to shear discrete pieces of the semi-fluid material and convey them suspended in the gaseous stream to the spray nozzle.

3. The apparatus'of claim 2 wherein the means for suspending the semi-fluid material includes a T-section with the base of the T" connected to the discharge port of the pump, with the conduit connected to one side of the top of the T", and wherein the compressed gas is delivered through the other side of the top of the T" for impingement at substantially right angles to the semifluid material extruded into the T-section by. the pump at a pressure sufficient to suspend discrete pieces of the semifluid material and convey them to the spray nozzle through the conduit.

4. Apparatus for spraying a continuous stream of a wet semi-fluid material capable of setting to a hard end product against a work surface comprising:

a spray nozzle,

a positive pump metering and pumping the semi-fluid material to the discharge outlet of the pump,

means for suspending the semi-fluid material delivered to the discharge outlet of the pump in a gaseous medium and delivering it to the spraying nozzle, said means including a conduit connecting the discharge outlet of the pump and the spray nozzle, and a means intersecting the conduit impinging a compressed gas at an angle to the stream of semifluid material extruded into the gas stream by the pump at a pressure sufficient to shear discrete pieces of the semi-fluid material and convey them suspended in the gaseous stream to the spray nozzle,

metering means for metering a dry, particulate quickset additive for the semi-fluid material in a predetermined weight ratio of additive to semi-fluid material,

a second conduit connecting the discharge outlet of the metering means intersecting the conduit carrying the stream of gas-suspended semi-fluid material before ejection of the semi-fluid material from the nozzle, and

means supplying compressed gas to suspend and convey the particulate additive into contact with the gas-suspended semi-fluid material.

5. The apparatus of claim 2 wherein the semi-fluid material is a cementitious material.

6. The apparatus of claim 4 wherein the metering means includes a holding vessel for the additive, agitator means within the vessel, and feed means in communication within the vessel for feeding predetermined amounts of additive into the second conduit.

7. The apparatus of claim 6 wherein the pump and metering means are directly connected for delivery of a predetermined weight ratio of semi-fluid material to quick-setting additive.

Claims

1. Apparatus for spraying a continous stream of wet semi-fluid material capable of setting to a hard end product against a work surface comprising: a spray nozzle, a positive pump metering and pumping semi-fluid material to a discharge outlet thereof, means for suspending the semi-fluid material delivered to the discharge outlet in a gaseous medium and delivering it from the discharge outlet to the spray nozzle, said means including a conduit connected between the discharge outlet of the pump and the spray nozzle, and means impinging a compressed gas at an angle to the stream of semi-fluid material metered from the discharge outlet into the conduit at a pressure sufficient to shear discrete pieces of the semi-fluid material extruded into the gaseous stream by the pump and convey them in the suspended gas stream to the spray nozzle.

2. Apparatus for spraying a continuous Stream of wet semi-fluid material capable of setting to a hard end product against a work surface comprising: a spray nozzle, a rotary pump for metering the semi-fluid material to a discharge outlet, the rotary pump including a stationary ring, a compressible hose having circumferentially placed inlet and outlet ports therein extending about and bearing against the interior surface of the stationary ring, and a power driven rotor compressing the hose and producing a fluid pocket of material moving about the circumference of the ring progressively from the inlet port for extrusion of the semi-fluid material through the outlet port, and means for suspending the semi-fluid material delivered to the discharge port by the pump in a gaseous medium and delivering it to the spray nozzle, said means including a conduit connected between the discharge port of the pump and the spray nozzle, and means impinging a compressed gas at an angle to the stream of semi-fluid material extruded into the conduit by the pump at a pressure sufficient to shear discrete pieces of the semi-fluid material and convey them suspended in the gaseous stream to the spray nozzle.

3. The apparatus of claim 2 wherein the means for suspending the semi-fluid material includes a T-section with the base of the ''''T'''' connected to the discharge port of the pump, with the conduit connected to one side of the top of the ''''T'''', and wherein the compressed gas is delivered through the other side of the top of the ''''T'''' for impingement at substantially right angles to the semi-fluid material extruded into the T-section by the pump at a pressure sufficient to suspend discrete pieces of the semifluid material and convey them to the spray nozzle through the conduit.

4. Apparatus for spraying a continuous stream of a wet semi-fluid material capable of setting to a hard end product against a work surface comprising: a spray nozzle, a positive pump metering and pumping the semi-fluid material to the discharge outlet of the pump, means for suspending the semi-fluid material delivered to the discharge outlet of the pump in a gaseous medium and delivering it to the spraying nozzle, said means including a conduit connecting the discharge outlet of the pump and the spray nozzle, and a means intersecting the conduit impinging a compressed gas at an angle to the stream of semi-fluid material extruded into the gas stream by the pump at a pressure sufficient to shear discrete pieces of the semi-fluid material and convey them suspended in the gaseous stream to the spray nozzle, metering means for metering a dry, particulate quick-set additive for the semi-fluid material in a predetermined weight ratio of additive to semi-fluid material, a second conduit connecting the discharge outlet of the metering means intersecting the conduit carrying the stream of gas-suspended semi-fluid material before ejection of the semi-fluid material from the nozzle, and means supplying compressed gas to suspend and convey the particulate additive into contact with the gas-suspended semi-fluid material.