US3758034A

US3758034A - Method for pneumatically placing semi-fluid materials

Info

Publication number: US3758034A
Application number: US00175462A
Authority: US
Inventors: J Broadfoot
Original assignee: Individual
Current assignee: Individual
Priority date: 1971-08-27
Filing date: 1971-08-27
Publication date: 1973-09-11
Anticipated expiration: 1990-09-11

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

United States atent [191 Broadfoot p [111 3,758,034 Sept. 11, 1973 METHOD FOR PNEUMATICALLY PLACING SEMI-FLUID MATERIALS [76] Inventor: John T. Broadfoot, 12714 Aurora Ave. N., Seattle, Wash. 98133 [22] Filed: Aug. 27, 1971 [21] Appl. No.: 175,462

Related US. Application Data [62] Division of Ser. No. 47,538, June 18, I970,

abandoned.

[52] US. Cl. 239/9 [51] Int. Cl. A62c' 1/12 [58] Field of Search 239/8, 9

[56] I References Cited UNITED STATES PATENTS 3,077,415 2/1963 Ayres 239/9 Primary Examiner-Lloyd L. King Attorney-Seed, Berry, Dowi'ey t k Cross [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 theT 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 PAIENIEnsm um SHEET 1 BF 2 JOHN T. BROIQDFOOT VENT OR; I

PAIENIEUSEH mm 3,758,034

SHEEI 2 BF 2 JOHN T- BROADFOOT INVENTOR.

METHOD FOR PNEUMATICALLY PLACING SEMI-FLUID MATERIALS This application is a division of Ser. No. 47,538, filed June 18, 1970, 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. i

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 timer 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. The principal 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 bythe nozzle operator during application. His judgement, or the lack of it, is the criteria used and the results generally obtained are less thanoptimum. In addition to this disad- 2 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 machine 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 vantage 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 surface applied 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 minim um 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, Mo. 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 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 delivering the mixed fluid and accelerator out 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. i

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. '1, the overall apparatus of this invention comprises aframe or base support 1 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 wherein the 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 U.S. 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 oribital 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 1 inch in diameter. The shaft of the pump is connected to a suit able 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, cement and aggregate. v

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 49 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 is rotated, more 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 secured 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 stifl 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-s'ection by the fluid pump and carries it through conduit 55 to nozzle from which 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 3 inches as shown in FIG. 1 and the base of the T-section has an internal diameter of about the same. The conduit55 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 to 2 inches there has been no difficulty in conveying the concrete for distances over 200 feet andup 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 predetermined 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 any any of these may be used. l

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, theaggregate having an average size of about /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 10 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 setsso quickly that even when water is flowing through an opening to be covered with concrete the hole can be coveredwithout the water affecting it. For example, in a tunnel through which a full flow ,of water 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 (l 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 concretebeing applied, (4) precontrol of water content of the concrete mixture, allowing optimum water content and ininimumrebound, (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 washedout. 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 usedin most applications is expensive and it is highly desirable to be able to control the amount of ac celerator used to minimize expense.

I claim:

l. A method of applying a concrete slurry incorporating a quick-setting additive to a work surface, the slurry setting to a hard concrete product within seconds after application, comprising:

metering, under pressure, a concrete slurry having a controlled amount of water added thereto to a discharge zone, conveying the slurry from the discharge zone to a discharge nozzle, pneumatically metering and conveyinga dry, particulate, quick-setting additive for the concrete slurry into the concrete slurry stream before ejection of the slurry from the discharge nozzle, the additive uniformly mixing with the concrete slurry before discharge from the nozzle. 2. A method of applying a concrete slurry incorporating a quick-setting additive to a work surface, the slurry setting to a hard concrete product within seconds after application, comprising:

metering, under pressure, a predetermined amount of a concrete slurry having a controlled amount of water added thereto to a discharge zone, impinging a compressedgas against the stream of concrete slurry entering the discharge zone at a pressure sufficient to shear discrete pieces of the concrete slurry and suspend them in the gaseous stream for conveying through a conduit to a discharge nozzle, and suspending a dry, particulate, quick-setting additive for the concrete slurry in a stream of compressed gas, the gas stream conveying theadditive through a conduit into the concrete slurry stream before ejection of the concrete slurry mixture from the discharge nozzle onto the work surface, the additive uniformly mixing with the suspended concrete slurry.

3. The method of claim 2 including controlling the weight ratio of concrete slurry to quick-setting additive.

4. The method of claim 3 wherein 2 to 8 percent by weight of quick-setting additive is added to the concrete slurry based on the weight of the cement in the concrete slurry.

5. The method of claim 3 wherein the quick-setting additive is mixed with the concrete slurry at a point ranging from 3 to 10 feet beforeejection of the concrete slurry from the discharge nozzle.

6. The method of claim 1 wherein the concrete slurry is metered under pressure by (1) admitting a concrete slurry in a compressible hose having inlet and outlet ports at the respective ends thereof, (2) compressing the hose beginning at the inlet port: and moving toward the outlet port to move a pocket of the concrete slurry contained therein progressively from the inlet port through the outlet port to the discharge zone.

7. A method of applying a concrete slurry incorporating a quick-setting additive to a work surface with setting of the concrete slurry-additive mixture to a hard end product within seconds after application, comprising:

admitting a concrete slurry into a compressible hose having inlet and outlet ports in the respective ends thereof,

comprssing the hose beginning at the inlet port and moving toward the outlet port to move a pocket of the concrete slurry contained therein progressively from the inlet port through the outlet port to a discharge zone,

and

conveying the additive suspended in the gas stream into the suspended stream of concrete slurry before ejection of the slurry-additive mixture from the discharge nozzle onto the work surface, the additive uniformly mixing with the suspended concrete slurry before discharge from the nozzle.

Claims

1. A method of applying a concrete slurry incorporating a quicksetting additive to a work surface, the slurry setting to a hard concrete product within seconds after application, comprising: metering, under pressure, a concrete slurry having a controlled amount of water added thereto to a discharge zone, conveying the slurry from the discharge zone to a discharge nozzle, pneumatically metering and conveying a dry, particulate, quicksetting additive for the concrete slurry into the concrete slurry stream before ejection of the slurry from the discharge nozzle, the additive uniformly mixing with the concrete slurry before discharge from the nozzle.

2. A method of applying a concrete slurry incorporating a quick-setting additive to a work surface, the slurry setting to a hard concrete product within seconds after application, comprising: metering, under pressure, a predetermined amount of a concrete slurry having a controlled amount of water added thereto to a discharge zone, impinging a compressed gas against the stream of concrete slurry entering the discharge zone at a pressure sufficient to shear discrete pieces of the concrete slurry and suspend them in the gaseous stream for conveying through a conduit to a discharge nozzle, and suspending a dry, particulate, quick-setting additive for the concrete slurry in a stream of compressed gas, the gas stream conveying the additive through a conduit into the concrete slurry stream before ejection of the concrete slurry mixture from the dischArge nozzle onto the work surface, the additive uniformly mixing with the suspended concrete slurry.

5. The method of claim 3 wherein the quick-setting additive is mixed with the concrete slurry at a point ranging from 3 to 10 feet before ejection of the concrete slurry from the discharge nozzle.

6. The method of claim 1 wherein the concrete slurry is metered under pressure by (1) admitting a concrete slurry in a compressible hose having inlet and outlet ports at the respective ends thereof, (2) compressing the hose beginning at the inlet port and moving toward the outlet port to move a pocket of the concrete slurry contained therein progressively from the inlet port through the outlet port to the discharge zone.

7. A method of applying a concrete slurry incorporating a quick-setting additive to a work surface with setting of the concrete slurry-additive mixture to a hard end product within seconds after application, comprising: admitting a concrete slurry into a compressible hose having inlet and outlet ports in the respective ends thereof, comprssing the hose beginning at the inlet port and moving toward the outlet port to move a pocket of the concrete slurry contained therein progressively from the inlet port through the outlet port to a discharge zone, impinging a compressed gas against the stream of concrete slurry entering the discharge zone at a pressure sufficient to shear discrete pieces of concrete slurry from the mass entering the discharge zone and suspend them in the gaseous stream for conveyance through a conduit to a discharge nozzle, suspending a dry, particulate, quick-setting additive for the concrete slurry in a compressed gas stream, and conveying the additive suspended in the gas stream into the suspended stream of concrete slurry before ejection of the slurry-additive mixture from the discharge nozzle onto the work surface, the additive uniformly mixing with the suspended concrete slurry before discharge from the nozzle.