ZA200205183B

ZA200205183B - Block forming apparatus.

Info

Publication number: ZA200205183B
Application number: ZA200205183A
Authority: ZA
Inventors: Joachim Kofahl; Quintin Booysen
Original assignee: Hydraform Internat Ltd
Priority date: 2000-02-09
Filing date: 2002-06-27
Publication date: 2004-03-24

Description

BLOCK FORMING APPARATUS

BACKGROUND OF THE INVENTION

THIS invention relates to apparatus for forming blocks such as building blocks, and to a method of making such blocks.

SUMMARY OF THE INVENTION

According to the invention there is provided a block forming apparatus comprising: a compression chamber having upper and lower opposed ends; a common inlet and outlet at the upper end of the compression chamber; a lower ram movable between an extended position in which it extends . into the compression chamber towards the upper end thereof, and a

CONFIRMATION COPY retracted position towards the lower end thereof; and an upper ram movable between an open position in which the compression chamber can be charged with block forming material, and a closed position in which it extends into the compression chamber to compress the block forming material from the top, wherein the upper ram is operable to compress the block forming material from the top before operation of the lower ram.

Preferably the upper ram is operated by a first actuator arranged so that the upper ram exerts a force which is substantially less than that exerted by the lower ram.

The first actuator may be arranged so that the force exerted by the upper ram is less than one half that exerted by the lower ram, and preferably approximately one third that exerted by the lower ram.

In a preferred embodiment, the first actuator may comprise a cylinder rated at between 2 and 4 tons, with the lower ram being operated by an actuator comprising a cylinder rated at between 4 and 8 tons.

The upper ram may be mounted on an arm which is movable pivotably about a bearing to raise and lower the upper ram.

Preferably, the first actuator is connected to the arm at a connection point between the bearing and the upper rams so that the distance between the upper ram and the connection point is less than the distance between the : bearing and the connection point.

The upper ram preferably has an operating stroke which is greater than that of the lower ram.

The operating stroke of the upper ram is preferably between 70 mm and 120 mm, and the stroke of the lower ram is preferably between 60 mm and 100 mm.

In a preferred embodiment of the apparatus, the stroke of the upper ram is approximately 100 mm and the stroke of the lower ram is approximately 60 mm, with the compression chamber being approximately 390 mm in length.

The first and second actuators may be operated from a common hydraulic circuit, at the same operating pressures.

The apparatus may include a loading aid connected on or adjacent the upper end of the compression chamber and having an outlet movable between an operative position above the inlet of the compression chamber, and an inoperative position adjacent the inlet of the compression chamber.

Further according to the invention there is provided a method of forming a block from a soil/binder mixture including the steps of: loading a charge of soil/binder mixture into an upright compression chamber, compressing the mixture from opposed ends of the compression chamber to form a block; and : ejecting the block from the compression chamber.

} wherein the mixture is first compressed from one end of the compression chamber and then compressed from the other end of the compression i chamber.

Preferably, the mixture is compressed by a first ram at a first, lower pressure and then by a second ram at a second, higher pressure.

The first, lower pressure may be less than half the second, higher pressure, and is preferably approximately one third of the second, higher pressure.

The operating stroke of the first ram may be greater than that of the second ram.

Preferably, the stroke of the upper ram is between 70 mm and 120 mm, and the stroke of the lower ram is between 60 mm and 100 mm.

In a preferred embodiment of the method, the stroke of the upper ram is approximately 100 mm and the stroke of the lower ram is approximately 60 mm, and the compression chamber is approximately 390 mm in length, so that a block is formed having a height of approximately 230 mm.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a pictorial view of block forming apparatus according to the invention;

Figures 2, 3,4 and 5 are partial sectional side views of the apparatus : in use; and

Figure 6 is a schematic diagram of a hydraulic control circuit of the apparatus.

DESCRIPTION OF AN EMBODIMENT

Figure 1 shows a block forming machine according to the invention, the heart of which is an upright compression chamber 10 having an upper end 12 and a lower end 14. The compression chamber is formed from heavy steel plate and is generally rectangular in section. The compression chamber 10 can be fitted with a removable liner, which can be grooved or otherwise shaped to impart a desired finish to blocks produced by the apparatus. The height of the compression chamber is 390 mm.

The compression chamber is mounted on a frame 16 and braced by means of gussets 18. Mounted below the compression chamber is a first double-acting hydraulic actuator in the form of a heavy duty hydraulic piston and cylinder 20.

The piston drives a lower ram 22 directly (see Figures 2 to 5) between a fully retracted position as shown in Figure 2 and a fully extended position as shown in Figure 5.

Fixed to the side of the compression chamber 10 opposite the gussets 18 are a pair of heavy plates 24 which serve both a reinforcing function and as a mounting for an arm 26 which is pivoted to the plates 24 by means of a heavy duty sleeved bearing 28. Mounted to the end of the arm 26 remote from the bearing is an upper ram 30 which is movable with the arm 26 between the fully retracted position shown in Figures 1 and 2, in which the upper end 12 of the compression chamber 10 is open, and the fully closed position shown in Figure : 4. In the latter position, the ram 30 extends into the interior of the compression chamber towards the lower end thereof, as is discussed below.

. A second double-acting actuator in the form of a hydraulic piston and cylinder arrangement 32 is mounted between the base of the plate 24 and a pivot pin } 36 between the ends of the arm 26, so that operation thereof raises and lowers the arm 26. In the prototype machine, the distance between the bearing 28 and the pivot pin 36 was 320 mm, and the distance between the pin 36 and the center of the ram 30 was 180 mm, the effect of which is discussed below. The cylinder 32 is substantially smaller than the cylinder 20, having typically in the region of half its rating. For example, the main cylinder 20 preferably is rated at about 4 to 8 tons, so that the cylinder 32 will typically be rated at about 1.5 to 2 tons at the maximum operating pressure of the hydraulic system of the apparatus.

In the prototype apparatus, the main cylinder 20 has a bore of 80 mm, a 50 mm diameter rod, and a stroke length of 410 mm. At an operating pressure of 8 MPa it generated a force of 4103 kilograms, while at 13 MPa it generated a force of 6668 kilograms.

The second cylinder 32 had a bore of 63 mm, a rod diameter of 25 mm and a stroke of 240 mm, and is rated to develop a force of 2144 kilograms at 8 MPa and a force of 3484 kilograms at 13 MPa.

As best shown in Figure 1, a loading aid 38 in the form of a small hopper with an open bottom (or a funnel) is mounted pivotably by means of a pin 40 and a sleeve 42 so that it can be rotated from the operative position shown in Figure 1, in which it is out of the way of the ram 30, into an operative position in which it is directly over the upper end 12 of the compression chamber 10, as indicated in Figure 2. In this latter position, the loading aid assists an operator of the apparatus in filling the compression chamber 10 with a suitable soil/binder mixture (typically a soil/cement mixture). Once the compression chamber has been filled, the loading aid is swung out of the way. The lower edge of the loading aid tends to clear away any excess soil/cement mixture,

E WO 01/58654 PCT/IB01/00155 helping to ensure that the compression chamber is filled with the correct amount of material.

Using a pair of control levers 44 and 46, which control the cylinder 32 and the cylinder 20, respectively, the apparatus is now operated as foliows. Firstly, as indicated in Figure 3, the cylinder 32 is operated to lower the arm 26 so that the upper ram 30 enters the compression chamber to a distance of between 70 and 120 mm (preferably about 100 mm) and compresses the soil/cement mixture 48 therein. Due to the unequal distances between the pivot pin 36, the bearing 28 on the one hand and the center of the ram 30 on the other hand, the effective force applied to the soil/cement mixture by the ram 30 is somewhat reduced, to 1371 kgs at an operating pressure of 8 MPa and 2229 kgs at the higher operating pressure of 13 MPa .

The end face of the ram 30 travels down into the compression chamber before the lower edges of the arm 26 come to rest against the upper edges of the compression chamber, limiting the travel of the ram 30 to about 100 mm as mentioned above. At this point, the control lever 44 can be released. This closes the valve supplying the cylinder 32. The cylinder 32 is filled with hydraulic fluid and is effectively “locked” in position when its control valve is closed. At this stage, assuming that the compression chamber had been completely filled with soil/cement mixture 48 to its full length of 390 mm, the overall height of the partially formed block in the compression chamber between the two rams will now be 290 mm.

The operator now operates the control lever 46, operating the cylinder 20 to raise the lower ram 22, thus compressing the soil/cement mixture 48 from below. As mentioned above, the force exerted by the lower ram varies between 4103 kgs and 6668 kgs, depending on the operating pressure of the hydraulic system, which in the prototype can vary between 8 and 13 MPa. : The travel of the ram 22 on its compression stroke is typically 60 mm to 100

. mm, so that the soil/cement mixture is compressed by a total of 160 mm to 200 mm. Assuming a total compression of 160 mm, the height of the finished block will thus be 230 mm, which is a preferred standard size.

Conventionally, it has been found that compaction of a layer of soil/cement mixture of greater than 300 mm depth is not successful. However, due to the dual action of the apparatus of the invention, with its pre-compaction and main compaction strokes, a layer of soil/cement mixture having a depth substantially greater than 300 mm can be compacted successfully, resulting in a usefully large block.

Due to the characteristics of the soil/lcement mixture used to manufacture blocks in the apparatus, the pre-compression of the mixture by the upper ram enables the relatively lower compressive force exerted by the upper ram 30 to counterbalance the higher force exerted by the ram 22, which otherwise would be resisted entirely by the “locked” cylinder 32. Due to the lever effectively created by the location of the pin 36 relative to the bearing 28 and the center of the ram 30, the absence of this effect could result in excessive pressures being developed in the cylinder 32. The compression of the material 48 from both ends of the compression chamber helps to ensure a more even pressure distribution in the block as it is being compressed, resulting in building blocks with more uniform density compared with blocks compressed from a single end.

As a final stage in the block making process, illustrated in Figure 5, the cylinder 32 is operated to raise the arm 26 and to move the upper ram 30 clear of the upper end 12 of the compression chamber, and the cylinder 20 is then operated to extend the ram 22 through the compression chamber and partially . out of the upper end thereof, expelling the block of material 48 and allowing it to be removed easily.

Figure 6 shows a hydraulic control circuit for the above described apparatus.

The control system includes a sump 50 for hydraulic fluid, which in the prototype apparatus comprises a 140l tank. The tank is provided with an oil level indicator 52 and a breather outlet 54. A pump 56 is shown coupled to drive means “M” which is preferably a dedicated motor. A filter or strainer 58 connected to the inlet of the pump protects the hydraulic circuit from contaminants in the tank 50.

The output of the pump is connected to first and second manual control valves 60 and 62 and to a pressure gauge 64. The valve 60 controls the main hydraulic cylinder 20 which powers the lower ram 22, while the valve 62 controls the hydraulic cylinder 32 which controls the upper ram 30. The two cylinders thus share a common hydraulic circuit and operate at the same pressure. An adjustable pressure control valve 66 is provided to regulate the maximum output pressure of the valves, thus determining the force/pressure applied by the ram 22 and 30 in use. As mentioned above, an operating range of between 8 MPa and 13 MPa was selected for the prototype apparatus, according to the forces required by the rams and the maximum safe operating pressures of the cylinders.

The hydraulic circuit is completed by a return line to the sump 50 with a filter

Claims

« -10 - CLAIMS

1. A block forming apparatus comprising: a compression chamber having upper and lower opposed ends; a common inlet and outlet at the upper end of the compression chamber; a lower ram movable between an extended position in which it extends into the compression chamber towards the upper end thereof, and a retracted position towards the lower end thereof; and an upper ram mounted on an arm which is movable pivotably about a bearing between an open position in which the compression chamber can be charged with block forming material, and a closed position in which it extends into the compression chamber to compress the block forming material from the top, wherein the upper ram is operable to compress the block forming material from the top before operation of the lower ram, wherein the upper ram is operated by a first actuator arranged so that the upper ram exerts a force which is substantially less than that exerted by the lower ram.

2. Block forming apparatus according to claim 1 wherein the first actuator is arranged so that the force exerted by the upper ram is less than one half that exerted by the lower ram. Amended 13 June 2003 a.

3. Block forming apparatus according to claim 2 wherein the first actuator is arranged so that the force exerted by the upper ram is approximately one third that exerted by the lower ram.

4. Block forming apparatus according to claim 3 wherein the first actuator comprises a cylinder rated at between 2 and 4 tons, and the lower ram is operated by a second actuator comprising a cylinder rated at between 4 and 8 tons.

5. Block forming apparatus according to claim 4 wherein the first actuator is connected to the arm at a connection point between the bearing and the upper ram so that the distance between the upper ram and the connection point is less than the distance between the bearing and the connection point.

6. Block forming apparatus according to any one of claims 1 to 5 wherein the upper ram has an operating stroke which is greater than that of the lower ram.

7. Block forming apparatus according to claim 6 wherein the operating stroke of the upper ram is between 70 mm and 120 mm, and the stroke of the lower ram is between 60 mm and 100 mm.

8. Block forming apparatus according to claim 7 wherein the operating stroke of the upper ram is approximately 100 mm and the stroke of the lower ram is approximately 60 mm, and wherein the compression chamber is approximately 390 mm in length. Amended 13 June 2003

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9. Block forming apparatus according to any one of claims 1 to 8 wherein the first and second actuators are operated from a common hydraulic circuit, at the same operating pressures.

10. Block forming apparatus according to any one of claims 1 to 9 including a loading aid connected on or adjacent the upper end of the compression chamber and having an outlet movable between an operative position above the inlet of the compression chamber, and an inoperative position adjacent the inlet of the compression chamber.

11. A method of forming a block from a soil/binder mixture including the steps of: loading a charge of soil/lbinder mixture into an upright compression chamber; compressing the mixture from opposed ends of the compression chamber to form a block; and ejecting the block from the compression chamber; wherein the mixture is first compressed from one end of the compression chamber by a first ram at a first, lower pressure and then compressed from the other end of the compression chamber, by a second ram at a second, higher pressure, wherein the first, lower pressure is less than half the second, higher pressure.

12. A method according to claim 11 wherein the first, lower pressure is approximately one third of the second, higher pressure. Amended 13 June 2003

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13. A method according to either of claims 11 or 12 wherein the operating stroke of the first ram is greater than that of the second ram.

14. A method according to claim 13 wherein the operating stroke of the first ram is between 70 mm and 120 mm, and the stroke of the lower ram is between 60 mm and 100 mm.

15. A method according to claim 14 wherein the operating stroke of the upper ram is approximately 100 mm and the stroke of the lower ram is approximately 60 mm, and wherein the compression chamber is approximately 390 mm in length, so that a block is formed having a height of approximately 230 mm. Amended 13 June 2003