The invention relates to a concrete block molding machine comprising
A concrete block molding machine of the above-mentioned kind is known from US-A-4,312,242. The vibration assembly of this machine cannot be adjusted during operation.
GB-A-2,108,235 and AT-A-375 845 both disclose vibration assemblies that can be adjusted during operation.
The weights of the machine disclosed in GB-A 21 08 235 are driven by one pin which is exposed to the elements. There is no rigid central support shaft to support the weights and to transfer vibrations. An outer drum is supported by bearings which are supported by an inner drum.
The vibration member disclosed in AT-A-375 845 has a hollow central shaft and a tube member supported on the hollow central shaft by bearings. Weights are attached directly to the hollow shaft and to the tube member. A single pin drives the weights provided on the tube member.
In prior art machines in which the eccentric shafts producing the vibration have been stopped to halt the vibration at the end of the densifying step, large brakes have been required to stop the shafts. Moreover, because of the rapid acceleration and deceleration required in contemporary high production machines, as much as four times the horsepower required to produce the vibration had to be utilized, with the result that much larger motors and shafts were required for reasons other than producing the vibration. In machinery of the type disclosed in US-A-4 312 242, the vibrating shaft in effect coasts between intervals of operation of the drive motor and so need not be braked and brought up to full speed from a static position. However, the machine still operates by starting and stopping the drive motor and a substantial acceleration of the coasting shaft is required at the time it is desired to produce vibration. Moreover, such prior art machinery is not versatile in the sense that the amplitude of vibration and the forces exerted can be varied during the vibration portion of the cycle.
The invention is directed to a high speed, concrete products forming machine which can be utilized in production operations for manufacturing a variety of shapes from a variety of aggregates. Certain intensities and patterns of vibration are optimally used for any given mold, shape of product, or aggregate mix which is used.
It is the object of the present invention to provide a machine and a method which encourage the programming of the best cycle parameters for a particular "run" so that the same parameters can be stored in the memory of a programmable logic controller and used in future runs of a particular product.
Furthermore, it is the object of the invention to provide a system in which the vibrating shaft assembly can be rotated continuously at vibrating speed without the need for intermittent starting, stopping, and braking while providing the capability of changing the amplitude of the vibration during the operating cycle, and even during the product densifying portion of the cycle.
According to the invention this object is solved by a machine characterised by the following features:
Further improvements of this machine are subject matter of claims 2 to 7. Claims 8 to 16 relate to the method of molding concrete blocks in accordance with the present invention.
of The invention provide a system of the character described which utilizes a pair of vibrating shaft assemblies which can be so controlled that the vibration occurs in absolute synchronism.
In this system the amplitude of vibration can be varied during the cycle to compensate for the fact that the total weight of the molding system being vibrated changes during the forming cycle.
The invention provides a system which contains a shaft assembly whose strength is not compromised intermediate its span, and which can compactly handle the high loads involved in a most efficient and reliable manner.
Furthermore, the invention provides a quiet system which provides a high density block with low power consumption, and consequently is economical to operate.
According to the invention the system utilizes a spring having a predetermined rate to opposing the axial movement of the weight position adjusting piston-cylinder assembly in a manner such that the spring mechanism is operative to restore the vibration inducing mass to a desired or null position.
An embodiment of the invention is shown in the accompanying drawing.
Referring now more particularly to the accompanying drawing and in the first instance to Figure 1, a block making machine, generally designated M, of is illustrated fragmentarily. The machine may be considered to include a multi-compartmented mold box, generally designated 10, comprising side members 10a, end members 10b, and divider or partioning plates 11. In addition, core members 12, such as roof top cores, are provided in the compartments defined by the divider plates 11 for the purpose of forming the core openings in the concrete blocks which may, for example, be formed in this particular mold box.
The lower end of the mold box 10 is, during the forming cycle, closed by a vertically raisable pallet which is releasably clamped to the lower end of the mold box to vibrate with it by a raisable platen having a rubber block top. The upper end of the mold box is open to the reception of concrete mix material from a feed box at the beginning of the cycle. Stripper members are utilized in the usual manner at the end of the cycle to push the blocks formed from the mold as the pallet lowers to a conveyor which moves the green block to a curing area such as a kiln.
As shown, the mold box 10 has mold supporting side arms forming vibratible frame 13. Spanning the ends of the side arms are twin vibrator shaft assemblies, each generally designated S, and being shown more particularly in Figures 2 and 3. As illustrated, a shaft assembly S is provided at each end of the mold box and both vibrating shaft assemblies are controlled to operate synchronously so that one end of the mold is not vibrated more intensely than the other. This is necessary to ensure uniformity in the blocks being formed in the mold. As Figure 2 particularly indicates, the side arms of the frame 13 support bearings 14 which journal each shaft S for rotation. Each shaft assembly S incorporates a shaft 15 which, at one end, has a solenoid operated variator drive sheave 16 fixed to it in the usual manner for receiving a drive belt 17. Drive belts 17 are driven by an electric, or other suitable, motor in the usual manner at the same speed of rotation but the speed of rotation of each may be adjusted equally with adjustment of the sheaves 16. Mounted on each of the drive shafts 15 to rotate therewith, are opposite end stubs 18 and 19 which, it will be noted in Figure 2, have portions eccentrically disposed relative to the axis x to provide offset weight portions 18a and 19a. Locking ring assemblies 20 secured by bolts 21 are provided in end recessed portions 22 in the end stub 18 and 19 to unite the shaft 15 and the end stubs 18 and 19 for conjoint rotation. The end stubs 18 and 19 are also recessed as at 23 to receives roller bearings 24 supporting a circumferentially movable collar 25 which also as a weight portion eccentric with respect to axis x and forming a balancing mass 25a which is equal in weight to the combined weigth of eccentric portions 18a and 19a of end stubs 18 and 19. The offset weights of the collar 25 and end stubs 18 and 19, thus, balance one another in the Figure 2 position when the balancing mass 25a is 180° removed from the eccentric portions 18a and 19a of end stubs 18 and 19.
The inner end of end stub 19 is concentrically bored to form a cylinder C in which the reduced end 26a of a shouldered piston 26 is received. At its opposite end, piston 26 is annularly recessed as at 27 to provide a spring well for one end of a coil spring 28 whose opposite end is received in a spring well 29 provided in the end stub 18. Axial guide pins (not shown) may be provided for the spring 28.
Weight collar 25 is rotatable on bearings 24, from a position 180° removed from the eccentric portions of end stubs 18 and 19 in which the balanced condition is achieved and no vibration is transmitted to bearings 14, through 180°, for example, to a position in which maximum vibration is transmitted to the bearings 14 because the eccentric weight portions 18a, 19a and the balancing mass 25a are in a position of circumferential alignment.
Provided in the collar 25, is a bore 30 receiving a roller 31 mounted on a pin 32 whose inner end is received in a helical groove 33 provided in the piston 26. The helical groove 33 extends 180° in piston 26 to rotate collar 25 from a null position to a position in which maximum vibration is achieved, when the piston 26 is moved from the null position in which it is shown in Figure 2 from right to left against the bias of spring 28.
Provided in the shaft 15, is an axial bore 34 connecting with the radial bore 35 leading to the one end 26b of cylinder C. It is to be understood that air under a controlled pressure may be transmitted through a stationary coupling 36 within which reduced shaft end 15a is rotatable. While air is disclosed as the pressure transmitting medium it should be understood that other suitable fluids may be employed. As Figures 1 and 2 indicate, an air hose 37 leading to each shaft assembly S from air dispensing valve 38 is employed to supply air under the pressure desired for a particular operation to the cylinder C. Solenoid operated valve V, which has ports venting to atmosphere, is controlled by a programmable logic controller PLC. Spring 28 is of a predetermined rate, and its compression to the desired degree to achieve the intensity of vibration desired, is determined by the pressure of the air admitted via bores 34 and 35. This pressure is varied by the control 38 during each cycle of the machine when it is determined, for instance, to operate the machine in accordance with a cycle such as disclosed in Figure 4 (which will be later described). Seal rings 39 are provided to seal the cylinder C. The capability that the machine enjoys of achieving optimum intensity of vibration for the particular operation being performed, provides a machine which can often be adjusted to decrease the noise of operation of the machine, where this is desirable. The machine is capable of vibration at an increasing intensity during the filling of the mold from a feed box FB to achieve the desired uniformity of filling which promotes uniformity in the compaction portion of the cycle.
A typical cycle of operation is diclosed in Figure 4 where it will be noted that approximately a half a second is required to move the material feed box over the empty mold. During this time, each drive shaft 15 is being continuously driven at the selected speed by drive sheave 16 and the collar 25 of each shaft assembly S is in the position indicated in Figure 2 in which the balancing mass 25a of collar 25 counterbalances the eccentric portions 18a and 19a of end stubs 18 and 19 which rotate with the shaft 15. When the feed box is in position, air under the predesignated pressure, is fed from the valve 38 through bores 34 and 35 to move the pistons 26 from right to left in Figure 2 to the extent of 70% of their permissable movement. This revolves the collar 25 through about 126° and achieves an intensity of vibration equivalent to about 70% of maximum, due to the composite offset effect of the balancing mass 25a of collar 25 with respect to the eccentric portions 18a and 19a of end stubs 18 and 19. This intensity is increased slightly before rising to full intensity. The spring 28 of predetermined rate controls the axial position of piston 26. With this sytem as, for instance, opposed to a double-acting hydraulic system, there is no need to return oil to a reservoir (which takes time). Further the presence of air in a hydraulic line, variations in oil temperature, and line leaks, which all can affect the metered volume are not problems. The control achieved is particularly critical in machines in which a pair of shafts must operate in synchronism and a common valve needs to be used to ensure that they actuate at the same instant.
Figure 4 demonstrates that filling is completed in two seconds and the air pressure admitted through bores 34 and 35 is increased to move the piston 26 further from right to left to a position in which the balancing mass 25a of collar 25 and the eccentric portions 18a and 19a of end stubs 18 and 19 are in alignment so that maximum vibration is exerted during rotation of the shaft assemblies S. At the end of four seconds the supply of air through bores 34 and 35 is cut off, and the air pressure in these bores is bled to atmosphere via valve 38 so that spring 28 restores the piston 26 to the Figure 2 position with balancing mass 25a and eccentric portions 18a , 19a now in a balanced or null position. No vibration is transmitted via the bearings 14 to the mold box 10 at this time when stripping of the product from the mold is being accomplished, even though the shaft 15 continues to be driven at the designated speed. With the present construction, the drive belts 17 need not be started and stopped, and no brakes need be utilized. The vibration obtained is virtually vertical in character with no destabilizing lateral characteristics.
While one cycle has been illustrated, many others will be used. Typically filling will take place in from 3/4 to 2-1/2 seconds and compaction from 1-1/2 to 3-1/2 seconds. The speed of rotation of shafts 15 can also be varied by the PLC via adjustment of the sheaves 16 to change the frequency of vibration. The program for a given operation will consider both the frequency and amplitude of vibration.
In an alternate operation which is indicated by the chain lines in Figure 4, the intensity of vibration during the time of compacting vibration may be varied in the manner indicated at y, for example, for a particular product. The change may be made while the machine is operating.