US1766911A - Manufacture of cement concrete and apparatus for use therewith - Google Patents

Description

.June 24, 1930.

A. C. KNIFE MANUFACTURE 01-" CEMENT concg'sm AND APPARATUS FOR uss THERBVIITH Filed Nov. 29. 1926 s sheets-sum i mlmiil i'lllllllllllllllllllh:

June 24, 1930. A. c. KNIPE 1,766,911

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IANUFACTURE OF CEMENT CONCRETE AND APPARATUS FOR USE T HEREWITH Filed Nov. 29, 1926 5 Sheets-Sheet 3 is v 13 20' Y rfl 26 25 a. a X fi;

Patented June 24, 1930 UNITED stares mm orrics v ARTHUR CYRIL KNIFE, OF WESTMINSTER, LONDON, ENGLAND, ASSIGN'OR IIZO MODERN CONCRETE DEVELOPMENT COMPANY LIMITED, OF LONDON, ENG-LAND MANUFACTURE OF CEMENT CONCRETE AND APPARATUS FOR USE THEREWITH Application filed November 29, 1926, Serial No.

This invention relates to the manufacture of cement concrete and to apparatus foruse therewitli. y

'111 the manufacture of concrete as generally practised, owing to the thorough mixing of the ingredients which is absolutely neces sary, a comparatively large volume of it'- becomes entrapped in the mass with the resultthat the concrete when set possesses numerous voids or pores which are inimical to the strength of the article or structure produced, even though while mixing, the ingredients have been properly graded.

The object of the present invention is to avoid the consequences of such an aeration of the concrete and to so mix it that the mass will become very dense and therefore stronger and the tendency for it to sweat will belargely overcome. The invention consists in withdrawing or exhausting the entrained air while the ingredients are being mixed in the wet state.

The invention alternatively consists in mixing the wet ingredients of cement concrete in a chamber wherein a suitable degree of sub-atmospheric pressure exists or is maintained. c

The invention also consists in the combination of a cement concrete mixing chamber capable of being hermetically closed with a vacuum pump and a valved connection between the two, a

The invention will now be described with reference to the accompanying drawings which illustrate two forms of concrete mix ing machinery to which the presentinvention has been adapted.

Figures 1 and 2 are respectively a side and end elevation of a paddleetype mixer in which the mixing tank is non-rotating.

Figures 3 and 4 are similar views of a 1'0- tary drum type mixer, and i H Figure 5 is a side elevation of a modified arrangement of the plant.

Referringto Figures 1 and 2, the mixing tank a normally rests upon a foundation plate 6. and is fitted with acover plate 0, a rubber or other sealing gasket (Z being provided between the cover plate and box. In order that the box may be hermetically sealed the light 151,560, and in Great Britain December a, 1925.

iron framework 0 of the machine-carries one end 7 of a toggle lever system 7 while the other end 7? is pivoted to thecover plate 0. A traversing screw 9 operated by a hand wheel 9 is used to expand or contract the toggle levers to either raise and open, or lower and close, the cover plate 0. The mixer shaft 72 passes by means of stuffing glands is into the interior of the tank and carries the usual'mixing paddles (not shown).

For driving the mixer shaft it a pair of fast and loose pulleys Z are carried on shaft m which in turn is supported in bearings provided in the supports a. The shaft 072 carries a sprocket wheel 0 which by means ofa sprocket chain 29 drives another sprocket wheel 9 mounted on a sleeve 1" rotating 011 shaft 1 carried by bearings in the same supports a. On the sleeve r a gear wheel 8 is carried which gears with a wheel t that is mounted upon one end of the driving shaft it.

By the above gear train a reduction drive upon the mixing shaft is secured and the .mixing tank is free to be tilted about the centre of shaft 7" to one side in order to discharge the mixed concrete,'.the spur wheel t revolvinglround pinion s to permit this. a: is a hand wheel which when operated will, by means of the gears a y and shaft u, operate the gear 1), w and cause the tank to be tilted about centre r. i

To exhaust air from the mixing tank an air pump 6 of suitableconstruction is carried on the same bedplate b and driven by the belt pulleys Z through multiplying gear wheels 7. The air is exhausted from the tank by'the suction duct 8, separator 9, duct 10 andfiexible branch 11, the end of which passes into the tank a through the cover 0. The branch 11 fitted with a vacuum gauge" 12 and a valve 13'to admit atmospheric pressure when opening the tank.

The operation of the machine is as follows After the concrete has been mixed in the usual way, the cover; plate 0 is forced down upon the. top of the tank by operating the hand wheel y so that the toggle mechanism f is contracted to thus make the jointpaire tight. The stop valve 13 being then closed the continued running of the machine will produce a sub-atmospheric pressure condition within the tank indicated by the gauge 12 whereby the mass therein will be given greater density and the air spaces or pores left therein will be greatly reduced and minimised. When the treatment is completed the valve 13 is opened and the toggle mechanism actuated to lift the cover plate clear of the tank, after which the hand wheel a; is actuated to tilt the tank so that the contents may be discharged.

If desired, a clutch device generally denoted by 27 may be arranged on the power shaft so that the mixer may be operated independently of the air pump or both may operate together. Such clutch is operable by means of lever 28 as shown.

Referring now to Figures 3 and 4, the rotary drum mixer is is driven circumferentially by any suitable power unit, and the wheels 15 support the drum on a suitable foundation 16 upon which is erected a light framework 17 for the parts of the machine. 1 ach side of the drum has an opening for feeding and discharging the drum adapted to be closed by a circular cover plate 18 adapted to be sealed hermetically as before. Each door is centrally fitted with a trunnion piece 19, having a central bore extending. therethrough. and to support each door a radial arm 20 is provided. One end of such arm engages its corresponding trunnion piece 19 by means of a suitable ball bearing not shown,. while the other end is hinged upon a vertical pin 21 supported by a small bracket secured to the machine framework 17. The upper end of the vertical hinge pin carries a worm wheel indicated at 22 in gear with a worm 23. Both worms are fitted upon a shaft 23 extending from one side of the drum to the other and are operated by the hand wheel 24. The two worms are rightand left-hand respectively and the arrangement is such that by turning the'hand wheel both of the cover plates 18 are simultaneously actuated to cover or uncover the respective openings in the sides of the drum.

A flexiblepipe 25 and 26 is connected respectively to the outer ends of the trunnion pieces 19, one pipe being the vacuum pipe and the other being in communication with a water supply to feed water into the drum.

The arrangement of the air pump separatorand other details may be the same as that describedin the first modification but are not here described.

From the foregoing it will be understood that both cover plates may be hermetically closed upon the drum openings by the worm gear and will revolve with the drum in their ball bearings in the ends of the radial arms. When de-aeration is accomplished, both cover plates may be swung open clear of the usual feed or discharge mechanism.

To efiect a quick release of the doors a suitable clutch device generally indicated at 29 under the control of hand lever 30 may be combined with the hinge pins 21 so that the doors may be swung clear by hand out of the way of the feed or discharge mechanism.

It is to be understood that if necessary the concrete may be de-aerated in a chamber separate from the usual mixing chamber and an example of such an arrangement is shown in Figure 5.

According to this a rotary drum mixer 31 is driven by an electric motor 32 through suitable gearing such as the spur wheels 33, the mixed concrete being discharged through the inclined chute 34, this being all according to standard practice. A further chute 35 supported on a bracket 36 pivoted at 37 conducts the material. from chute 34 to the separate de-aerating chamber 38, the chute 35 being adapted to be swung around the pivot 37 away from the chamber 38 so as to allow the cover 39 to be fitted on to the deaerating chamber 38. Such cover is raised and lowered by the toggle linkage system i1 as already described with reference to Figures 3 and a. To actuate the de-aerator an electric motor a2 is provided which by means of a worm gear box 43 and gearing a 9 ist and ie drives a shaft f6 that passes into the de-aerator chamber 38. Such shaft carries suitable agitating devices not shown to energetically stir up the concrete. The electric motor 42 also drives by means of a clutch 47 an air pump 48. i

The mixer 31 having discharged the mixture into the de-aerator chamber 38, the chute 35 is swung out and the cover 39 lowered and tightly closed by means of the toggle links. The clutch a7 is then put into gear to drive the air pump 48, which by means of duct 49 in dotted lines withdraws air from the de-aerating chamber. Suitable means are provided for tilting the deaerator or otherwise removingthe concrete thus treated. 50 shows a hand brake for controlling the speed of the agitator.

In a large plant several mixers may be served by a single air exhausting means and moreover with reference to Figures 3 and 4 suitable devices are provided to maintain the centres of the cover plates in line with the drum axis. t

From the foregoing it will be understood that the cement concrete manufactured in the manner described will be very dense in structure and therefore stronger which is of particular value-when the concrete is to be exposed to weather action or is subjected to abrasion such as on concrete roads Where both are present. 8 v

Another characteristic of such de-aerated concrete is that owing to the'absence of pores its liability to sweat is largely minimized.

Having now described my invention what I claim as new and desire to secure by Letters Patent is 1. The method'of producing densified, deaerated cement concrete consisting in mixing the ingredients in a vessel open to the air until a homogeneous mass isobtained then submitting the mass to agitation in a way to bring all portions thereof to the uppersurface of the mass and While being agi tated subjecting the surface of the mass to'a high vacuum until the air is extracted and after the air is extracted working the mate: rial under normal atmospheric conditions.

2. A cement concrete machine comprising a concrete mixing container, means to agitate the concrete in the container, means for admitting water to the concrete constituents, an exhaust pump to withdraw air from the concrete, said pump being operable whilst the concrete is being mixed,a clutch operable for connecting the agitating means or pump or both to a source of power, a cover plate on the container, operating mechanism for closing the cover plate air tight, a separator and a partially flexible pipe connectionarranged in series between the air exhaust pump and the container, and a tWo Way valve on said'pipe connection operative to allow either air to be exhausted from the container or to establish atmospheric pressure therein.

In testimony whereof I have signed my name to this specification.

ARTHUR CYRIL KNIFE.

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