US 3175477 A
Description (OCR text may contain errors)
March 30,1965 Y H. CHENEY 3,175,477
CONTROL MEANS FOR CONCRETE LAYING MACHINES Filed Dec. 6, 1960 2 Sheets-Sheet 1 l-I l! CONTROL MEANS FOR CONCRETE LAYING MACHINES Filed Dec. 6. 1960 2 Sheets-Sheet 2 United States Patent 3,175,477 CONTROL MEANS FOR CONCRETE LAYING MACHINES Alwyn Halley Cheney, 23 Vancouver Ave., Springbank,
This invention relates to control means for concrete laying machines.
It is already known to lay concrete by means of machines which move forward to leave the concrete in position, and as an example reference may be had to my earlier applications upon which Australian Patents 224,-
413 and 228,818 have issued.
From attempts which have been made earlier at laying pipes or curbing or the like, it has been shown that a large number of requirements must be met to achieve a satisfactory product. One great difiiculty which exists in getting satisfactory operation is removal of variations in the forward speed of the machine which lays the pipes or curbing or the like and inconsistencies in the feed of concrete aggregate or other material.
In cases where a switch or valve is used to provide an on-off control for drive means for a concrete laying machine, the inertia of the machine in stopping and starting introduces wide variations in pressure in the concrete being packed. I have found that for most purposes a suitable pressure is sixty pounds per square inch applied to a wet mix of concrete being packed. If the pressure variation is maintained within plus or minus five pounds per square inch, a homogeneous product is formed, and after three weeks of ageing, a compressive strength of approximately six thousand pounds per square inch for a standard 4:2:1 mix has been achieved. If the pressure is allowed to fall below forty pounds per square inch, the strength decreases, while if the pressure exceeds eighty pounds per square inch, practical difliculties are encountered in the extrusion or packing of the wet mix.
The present invention seeks to overcome the difficulties which have been experienced heretofore in maintaining a comparatively steady pressure on concrete being packed to achieve a homogeneous and suitable product which will have the necessary strength throughout its length and in which variation of the product along its length will be reduced to safe values or will be completely removed.
According to my invention the improved product is attained by control means wherein forward motion of the machine is through a variable speed drive controlled through pressure sensitive means actuated by the pressure built up in the packed flowable material whereby a relatively uniform selected pressure is maintained on the material but speed of the machine varies in proportion to the volume of flowable material fed thereto.
It will be realized that the actual form of the invention can be very widely varied within the general spirit thereof, but to enable the invention to be fully appreciated an embodiment thereof will now be described with reference to the accompanying drawings, in which:
FIG. 1 is a schematic layout of a machine according to the invention,
FIG. 2 is a fragmentary perspective of such a machine, and
FIG. 3 is a central section through a throttle valve and its operating mechanism.
A machine 1 for laying curbing comprises a former 2 by means of which the product is shaped, the aggregate "ice being fed from a suitable hopper 3 to this former 2 by concrete packing means 4 consisting of a mandrel 5 surrounded by a helical blade 6 within the former 2, the mandrel 5 being driven by the mandrel drive motor 7 to worm the material from the hopper 3 to be extruded through the former 2.
The driven mandrel 5, instead of being simply fixed in bearings, is rotationally carried by bearings 10 which are supported by a pair of spaced parallel arms 12 'pivotally suspended from the sub-frame 11. Consequently, the mandrel 5 is free to move axially with respect to the sub-frame 11 as it revolves. Axial displacement of the mandrel 5 is resisted and sensed by pressure sensitive means which measures the thrust of mandrel 5 as it forces the aggregate into position in the former 2.
Flanges on the mandrel 5 prevent axial movement in the bearings 10 so that variations in the pressure exerted in an axial direction on the helical blade 6 as it forces the aggregate into the former is proportional to variations in axial displacement of the mandrel 5 with respect to the sub-frame 11 and such variations are used to vary the rate of forward drive of the machine 1.
The pressure within the concrete being packed is transmitted through a hydraulic master cylinder 16 to a hydraulic slave cylinder 17 by an enclosed hydraulic fluid containing line 18. The piston 19 of'the slave cylinder is loaded by spring 20, which spring applies pressure via the hydraulic pressure line 18 to the mandrel 5 of sixty pounds per square inch over the annular area defined by the helical blade 6. The slave piston rod 22 is coupled to the arm 23 of the throttle valve 24 which is placed in a by-pass circuit 25 across a variable speed hydraulic motor 26, the pressure hydraulic fluid being supplied by a vane type pump 27 driven by a gasoline engine 23. The frame 13 is mounted on wheels 30 engaging a track 31, and a chain 32 couples the frame drive motor 26 to one of the wheels 30. When the throttle valve 24 is fully open, it permits sufiicient by-pass of hydraulic fluid to prevent the frame drive motor 26 from operating, while if the valve is fully closed, the motor 26 operates at the maximum speed determined by the output of the pump 27.
It will however be realized that instead of allowing the mandrel itself to move forwardly to record these pressure factors in accordance with the above embodiment, the mandrel could be stationary and pressure measuring means such as a pressure sensitive finger could be associated with the mould itself which forms the curbing or pipe or other structure, or the whole of the laying section comprising the moulding mechanism as well as the feeding mandrel or the like can be mounted on the travelling frame by means of which it is carried to give pressure sensitive adjustment between this mechanism and the frame which can in turn be used to control the rate of forward drive of the frame.
The form of control to the throttle valve can also vary considerably. The mandrel 5 according to one embodiment is fitted with a thrust bearing against which a spring operates, urging the mandrel 5 in a rearward direction, and the plunger of a needle valve is movable with the thrust bearing, the needle valve functioning as the throttle valve.
One of the arms 12 may be extended upwardly to engage control means, either by means of a by-pass valve as disclosed in the above embodiment, or alternatively by control of the pump, if a pump of the displaceable axis type is used.
It has been found that when the laying of concrete or the like is pressure controlled by means of this invention, a much better product results which will be as nearly homogeneous as it is possible to get it and which is free from the cracking or voids which result where the product is not packed at the correct pressure.
Where pressure control is adequate it is possible to use a much drier miX for concrete products, the ratio employed being a 0.45 water/cement ratio, and this -en- 'sures that pipes or curbing or the like can be pressure moulded under conditions where they'will retain their shape because of the minimum amount of water present and therefore much higher finishes with better guarantee of homogeneity and absence of porosity can be assured. It has been found undesirable for the ratio to lie above 0.6 or below 0.3.
The mould 2 may extend beyond the outside of the. helical blade 6, but not by more than two inches in any' one direction without danger of strength and homogeneity loss. The mould 2 may not be disposed inwardly of the outside of the helical blade 6.
Obviously, instead of moving the machine forward by means of the stated control, the machine could be fixed and the means on which the concrete is being formed moved.
but being axially restrained against relative axial movement in said bearings, said mandrel being retained parallel to said concrete former by said spaced parallel arms, a helical blade on the mandrel, a mandrel drive motor coupled to said mandrel and arranged to drive said mandrel continuously; and control means comprising: a hydraulic master cylinder including a piston between said hinged arms and said frame, ahydraulic slave cylinder including a piston on said frame, an enclosed hydraulic fluid containing pressure transmitting line interconnecting said master and slave cylinders, a spring betweensaid slave cylinder and the piston therein, a throttle valve on the main frame coupled to said drive motor, and a link between said slave cylinder piston and said throttle valve, such that axial movement of said mandrel relativeto said frame both compresses said spring and also actuates said throttle valve to increase the speed of said drive motor thereby maintaining substantially uniform pressure on concrete extruded by said mandrel through said former irrespective of the rate of'concrete feed.
2. A machine according to claim 1 wherein a variable speed hydraulic motor constitutes said drive motor, the control means further comprising a hydraulic by-pass circuit across said variable speed from drive motor, said throttle valve being in said by-pass circuit.
.3. A machine according to claim 1 further comprising a hopper opening into said former for supplyin'g concrete thereto. 7
,4. A machine according to claim 1 wherein said mandrel has a constant diameter for substantially the entire length thereof. a, 7 I
5. A machine according to claim 1 wherein said helical stant for the entire length thereof.
blade has an outer diameter which is substantially con- References Cited bythe Examiner UNITED STATES PATENTS JACOB L. NACKENOFF, 'P'rham'Examiner.