Title of Invention

A DEVICE USEFUL AS A CONCRETE BLOCKMAKER

Abstract

A device useful as a concrete block maker which comprises a frame(l) consisting of a plurality of vertical pillars(2) having top and bottom cross bracings (3,4), a horizontal platform(5) rigidly fixed to a frame(l) at 2/3 height of the total height of the said frame, a plurality of vertical guide rods (6) being fixed between the said top and bottom bracings along two opposite sides of said frame(l), a yoke assembly (8) having a plurality of guides being placed in such a manner so as to slide along the said vertical guide rods(6), the said yoke assembly capable of being lifted/lowered by means (winch-10,wire rope-20, pulley-21), the said yoke assembly (8) being connected to mould frame (12) through a plurality of lifting pins(15) by means (tapered head-16, tapered hole-17, sleeve-18, bush-19), a mould block (7) having a plurality of mould cavity (7a) to hold concrete block (14) being rigidly fixed with the said mould frame (12) being provided with at least two form vibrators(13), a bridge (9) having a plurality of vertical plungers(22), variable dead weights (27) and guides (23) for guide rods(6) being placed above the said yoke assembly (8) such that the said yoke lifts the said bridge, the said bridge being provided with a hook (24) at its top for removable fixed to a release mechanism (25) and lever (26) fixed to the said bracing (3) of the said frame(l), a concrete feeder(ll) operated on a split two part (28,29), twin track (28) being placed along the top face of the said mould block (7) in such a manner so as to allow free up and down movement of the mould block (7) containing block cast (14) on pallet (30) placed in between the bottom of said mould block and the top of the said horizontal platform(5)

Full Text

The present invention relates to a device useful as a Concrete blockmaker. The device of the present invention is particularly useful for on-site production of large aggregate solid concrete blocks for construction of low cost housing. Concrete block walling has been used at many places as an alternative to traditional fired clay brick masonry. So far, mostly the hollow concrete blocks have been used for construction of filler walls and partition walls in multistoreyed framed buildings. The concrete used for these blocks have stone aggregates limited to a maximum size of 15mm. The walls made out of these hollow blocks have been no-load bearing type only because of the poor strength of the hollow block. Therefore the hollow blocks could be used only for limited application. In recent past, due to substantial increase in the price of fired clay bricks, serious problems have been encountered in hilly areas where fire clay bricks cannot be produced due to nonavailability of good clay and transportation of the bricks from plains adds further to the already increased price of the fired clay bricks. The problem of bringing out a suitable alternative to fired clay bricks for hilly and other areas of the country was studied at the Central Building Research Institute (CBRI) , Roorkee (India) and a new load bearing type large aggregate solid concrete block was introduced by CBRI in the market as an economical substitute to fired clay bricks for construction of building upto four storeys. The large aggregate solid concrete blocks are made from concrete mixes having stone aggregates of size about 50mm, coarse sand and cement. A series of lean concrete mixes can be used for production of these blocks. The nominal size of block is 30x20x15cm and weight about 18 kg. As per available test results the compressive strength of these blocks (using lean mixes i.e. 1:18) is more than 80 kg per sq.cm. These are therefore much stronger and economical in comparison to the traditional hollow concrete blocks. The large aggregate solid concrete blocks are more economical than even the fired clay bricks atleast in places like hilly areas & Rajasthan where good bricks are impossible to produce and these have to be transported from long distances. These blocks have already been used effectively and economically in the field during last over seven years in the construction of residential colonies and office buildings including Navodaya Vidalayas in different part of the country. It may be added here that in the present crises of food shortage, the earth consumed in making fired clay bricks should be saved for purpose of farming by encouraging the use of concrete blocks in place of bricks. So far, the large aggregate solid concrete blocks have been produced in the field by manual method using steel moulds and plate vibrator for compacting the concrete in the moulds. The method is very slow and there is large variation in strength and other characteristics from block to block. Available block making machines were tried to cast these blocks but these were found unsuitable for handling concrete with large aggregates of size 50 mm or around. To meet the growing demand for the said large aggregate solid concrete blocks, these were required to be produced on some suitable block making machine. The present invention is an attempt towards the development of an innovative block making machine suitable for making the aforesaid large aggregate solid concrete blocks. As regards prior knowledge of casting concrete blocks, there are two common methods (a) manual method and (b) machine method. In the manual method, blocks are cast by compacting concrete in a number of steel moulds arranged in a row. Compaction is achieved either by manual pocking of the concrete with steel rod or with the help of a plate vibrator placed manually on the top of the mould and run until the concrete in the mould is compacted thus forming the block. The manual method is not only slow, it also does not ensure proper compaction of concrete. The blocks produced are poor in quality with large variation in strength from block to block. In the machine method, casting of blocks is carried out with the help of a block making machine available in variety of designs. A block making machine in general comprises of following main features : (a) a mould or plurity of mould, (b) manual or power operated arranged for filling and screeding concrete in the mould, (c) some system for compaction of concrete in the mould to form a block there. (d) arrangement for ejecting the cast block from the mould. While there may be some variation in all the above four main features, (a) to (d) , in any two block making machines but by and large the feature which decides the size and compactness of a machine and makes the machine suitable for on-site production or for centralised factory production is the feature (c) i.e. compaction system. Concrete in the mould is compacted either by (i) pressing or by (ii) vibration and sometimes using even combination of both (i) & (ii) but the main method of compaction in any case has to be either pressing or vibration. The pressing type machines are large machines/or plants. These are cumbersome in handling and are very-costly. These are suitable only for large scale production units invariably installed in centralised factory. The vibration based machines are comparatively lighter and easily transportable and are therefore suitable for on-site production of blocks with medium production capacity. In US patent No.4802836, date 890207, Compaction Press for concrete block moulding machine has compaction shoes to fit into mould cells. Compaction shoes, equal in number to the number of cells in the mould, are sized, configured and positioned above the mould so that they may snugly fit into the mould cells. The shoes are mounted at the lower ends of the power jacks which are connected to a same fluid pressure source, or alternatively, are altogether in fluid communication. The power jacks are operated to move the compaction shoes or the concrete mix in the cells to apply to the mix in each cell, in the final cycle of vibration, an equal compaction pressure suitably selected to produce concrete blocks having a maximum equal density or more uniform desired or selected physical properties. With the mould held stationary, the support table or pallet may thereafter be moved down away from the mould to allow the concrete blocks to be dislodged from the mould by the downward movement of the compaction shoes. In another U.S. Patent No.4795334, dated 89 01 03, concrete block moulding machine which has a pair of presses slidably mounted on rail frame. The concrete block making machine includes a gate type frame constituting the body of the apparatus. A rail frame extends to the right and left from the gate type frame. A pair of presses are slidably mounted on the rail frame and adopted to move along the rail frame by the action of hydraulic cylinders that when one of the presses is on a moulding machine held by the gate-type frame, the other press is stationed at a position where a pressing head and a moulding box of a changeable mould assembly are changed, and resilient clampers by which the moulding box placed on the moulding machine is attached to a vertically movable table device. The patent basically covers a system of quick changing of moulds for casting variety of products. There are vibratory table machines comprising of a table with a vibrator fitted below it, and a structural steel frame to house and support the table. Mould filled with concrete is brought to the machine and placed on the table. The vibrator vibrates both the table and the mould. After compaction of concrete in the mould, the mould (with cast block) is removed from the table and taken away for purpose of demoulding. The pallet type stationary machines comprise of a vibratory platform housed and supported in a steel frame and a swiveling top plunger assembly attached to a pillar coupled with the machine frame. Mould is usually an integral part of the machine and is raised up and lowered down vertically with the help of some mechanical arrangement. Mould is filled with concrete either through a hopper fitted with the machine or by manual dumping of concrete directly into the mould. During working, a wooden or steel pallet or base plate, is placed on the vibratory platform. The mould is made to rest on the pallet. Concrete is filled in the mould and compacted through the vibratory platform. The top plunger is swivelled and brought in line with the mould and so adjusted that the top plunger touches the top face of the concrete mass compacted in the mould and it is locked there in this position. The mould is then lifted up. Due to the blockade provided by the top plunger,the cast block is left ejected on the pallet. Later the cast block alongwith the pallet is taken away to curing yard leaving the machine ready for next casting. The egg-laying type machines are essentially similar to the machines described in the foregoing paragraphs except that these are mobile in nature. Instead of ejecting the cast block on a pallet, these machines lay the blocks directly on a leveled concrete floor as hens lay eggs. After each operation of casting, the machine is moved forward to next position for next operation of casting/laying the block. In Indian Patent No. 149622 dated 9th November, 1978, "An Automatic Building Blocks Moulding Machine" relates to an automatic machine for the manufacture of building blocks from raw materials like non-plastic clays, soil-cement, laterite soil, lime and sand etc. under high pressure. The patented machine is a pressure based machine wherein the material in the mould cavity is pressed under high pressure (upto 500 kg per sq.cm) using a hydraulic system and then the blocks are ejected by using an another jack system. The machine functions in a cyclic fashion i.e. the raw material of block are fed at the first station, the blocks are moulded under high pressure at 2nd station, and the blocks are ejected at the 3rd station. Number of moulds are used travelling around the feeding, moulding and ejecting zones with the help of a powered conveyer system. The patented machine being a high pressure based machine is however not suitable for making blocks from concrete mixes with consistency varying from stiff to plastic. The concrete mixes of this range are in common use for making blocks for building purposes and are better handled on vibration based machines. In another Indian patent No. 162322 dated 24th March, 1983, "Method for Manufacturing a Machine Mould for Continuous Casting of Dry Wall Building Blocks and a Machine Mould so manufactured" is a patent on manufacture of mould boxes for extrusion of precast cement building blocks. The invention relates to a master form cast from a liquid casting compound (alkali base and acid hardner) wherein the pre-drilled metal liners (replaceable) are fitted inside to the female mould body resulting in a mould box of comparative dimensional accuracy. The mould box . so manufactured provides dimensional accuracy in casting of concrete and other blocks. The patent, however, does not describe anything about the production method of concrete blocks. There are quite a few drawbacks or limitations connected with hitherto known concrete block making machines. One of the biggest limitation is that there is no such machine available anywhere in the market which is capable of casting economical concrete blocks from concrete mixes having large aggregate, size 40 to 50mm. All the available block making machines are capable of handling concrete mixes with aggregate of largest size 15mm. Handling concrete mixes with aggregates larger than 15mm on these machines resulted in inadequate compaction and segregation of concrete mix during vibration. Since larger size aggregate helps in increasing the compressive strength of concrete even with leaner mixes of concrete, the. CBRI's large aggregate concrete blocks with aggregate about 50mm in size are therefore stronger and cheaper in comparison to traditional hollow concrete blocks where the aggregate size is limited to a maximum of 15mm. Concrete block making machines in general employ form vibrators for compaction of concrete in the mould. These vibrators are in some way connected to the forms or moulds in which concrete is compacted to give shape and size of the block. The available block making machines employ form vibrators which are high frequency (6000 vibration per minute, VPM) and low amplitude (below 0.5mm) type. It is a known fact that effectiveness of vibration depends mainly on the acceleration imparted by the form or mould to the concrete filled into it provided amplitude of the form is adequate. It has been observed that for concrete containing larger fractions of aggregate (size 40 to 50 mm) , greatest amplitude (1 to 1.5 mm) and acceleration around 8g are required for proper compaction of concrete. These parameters of vibration are not met by the available block making machines. Yet another drawback associated with the existing block making machines is poor compaction of concrete in mould (s) due to the loss of vibrational energy during transfer of vibrations from the vibrator to the mould. In these machines, the mould is bolted on the top face of a rectangular hollow steel frame such that the centre line of the mould is kept at a position little off the centre line of the said frame. A form vibrator is fitted at one extreme end of the said frame. For facilitating up and down movement of the said frame (and so also the mould and the vibrator), two guide bushes, one at the centre of each opposite longer side of the said frame are provided such that during working of the machine when the said frame is lifted up or brought down, these guide bushes slide up and down along two vertical guide rods, arranged in the centre of two opposite longer sides of the said frame and wherein the said two vertical guide rods form part of the structure of the machine. Another noteworthy point is that the said vertical guide rods are located in the centre of the two opposite sides of the said frame and are little off the centre with respect to the centre line of the mould mounted on the said frame. As mentioned earlier, this arrangement makes the vibrator located on one side of the frame and quite away from the mould. With this configuration of the vibrator-mould system, when vibrator is run, the vibrational energy is not transferred in its full extent to the mould as quite a part of this energy is dissipated to the entire machine through the said guide bushes and guide rod system. Also, the mould does not get uniform vibrations on all its sides; higher amount of vibrations is shared by that side of the mould which is on the vibrator side. Non-uniform and inadequate vibrations are thus transmitted to the mould and the result is poor compaction of the concrete. In US Patent No.4802,836 referred earlier, it has been mentioned that a uniform compaction pressure is maintained on the top of compaction shoes in each cell to produce concrete blocks having a maximum equal density from no slump concrete mixes to meet stiff specifications of CAN3-A 231,2 or ASTM C936-82 for concrete paving blocks for roads. Since the block making system developed under US Patent NO. 4 8 02,836, no-slump concrete is used and all physical properties of the blocks with -this concrete is directly related to the density of the block, the sole aim of the invention had therefore been to make blocks with uniform density only, while this feature of blocks works alright with paving blocks, the main requirement of concrete blocks for buildings is strictly the uniformity of size and not that strictly the density, although uniform density of block is preferred but not at the cost of stability of dimension. As per the US Patent NO. 4802,836, by maintaining uniform and same pressure on all the blocks during casting, uniform density of blocks can be achieved, but there will be definite variation (may not be very large) in the size (the height of blocks) which for building construction is not at all acceptable for obvious reasons of variation in the height of courses and non-uniform thickness of the mortar between the blocks. Another limitation of the US Patent No. 4802,836 is that it calls for an elaborate hydraulic system for giving uniform pressure on the blocks. Also the system calls for a takeoff conveyer for handling and transferring of blocks from the block making machine. These features make this block making machine suitable for centralised factory production only and unsuitable for the on-site production of blocks. The main object of the present invention is to provide a device useful as a concrete block maker which obviates the drawbacks of the hitherto known machines. Another object is to provide uniformity in both the density and dimensions of the cast blocks. Yet another object of the present invention is to provide a device for making concrete blocks using large aggregates size around 50mm. Still another object of the present invention is to provide a device for making concrete blocks using lean concrete mixes. Another object of the present invention is to provide a device for making concrete blocks with lower water cement ratio. Yet another object of the present invention is to provide a device capable of providing acceleration of about 8g and frequency of vibration and amplitude of around 3000 vpm and 1-1.5mm respectively to effectively handle and compact concrete mixes with large aggregate. Another object of the invention is to provide a device with vibration isolators introduced between the mould and the machine frame to ensure full transfer of vibrational energy from vibrators to the mould without dissipating or losing the vibrational energy through other parts of the machine. Still another object of the invention is to provide a device which ensures feeding of measured and same quantity of concrete in each mould cavity to maintain uniformity in the density and size of the cast blocks. The device of the present invention has been depicted in Fig. 1 to 4 of the schematic drawings accompanying these specifications. In Fig.l which shows the front view of the device, various parts are : 1. Skelton frame 2. Vertical pillar 3. Top cross bracing 4. Bottom cross bracing 5. Platform 6. Guide rod 7. Mould block 7a. Mould cavity 8. Yoke assembly 9. Bridge 10. Winch 12. Mould frame 14. Block 15. Lifting pin 20. Wire tope 21. Pulley 22. Plunger 23. Guide 24. Hook 25. Release pin 26. Lever 27. Dead weight 30. Pallets In Fig. 2 which shows the side view of the device, various parts are : 1. Skelton frame 2. Vertical pillar 3. Top cross bracing 4. Bottom cross bracing 5. Platform 6. Guide rod 8. Yoke assembly 9. Bridge 10. Winch 11. Concrete feeder 13 . Form vibrator 20. Wire rope 21. Pulley 23. Guide 24. Hook 25. Release pin 26. Lever 28. Track 29. Discontinuity 30. Pallets In Fig. 3 which shows the view of mould block lifting system, various parts are : 7. Mould block 8. Yoke assembly 12. Mould frame 15. Lifting pin 16. Tapered head 17. Tapered hole 18. Sleeve 19. Bush 28. Track In Fig. 4 (a) & (b) which show the view of block retaining system, various parts are : 2. Vertical pillar 8. Yoke assembly 9. Bridge 23. Guide 31. Double wedge fork 32. Sleeve 33. Pin 34. Cover 35. Compression spring 36. Pin 37. Sleeve 38. Base plate 39. Cross-channel 40. Wedge (bridge) 41. Wedge (Yoke) Accordingly the present invention provides a device useful as a concrete block maker which comprises a frame(1) consisting of a pherality of vertical pillars(2) having top and bottom cross bracings(3,4), a horizontal platform(5) rigidly fixed to the said frame(1) at appropriate height, a plurality of vertical guide rods(6) being fixed between the top(3) and bottom(4) bracings along two opposite sides of said frame(l), a yoke assembly(8) having a plurity of guides being placed in such a manner so as to slide along the aforesaid vertical guide rods (6) , the yoke assembly capable of being lifted/lowered by means (10,20 & 21), the yoke assembly(8) being connected to a mould frame(12) through a plur^Lty of lifting pins by means (16,17,18,19), a mould block(7) having a plurality of mould cavity(7a) to hold concrete block(14) being rigidly fixed with the said mould frame(12) which skirts around the mould block(7), the said mould frame(12) being provided with atleast two form vibrators(13), a bridge(9) having a plurality of vertical plungers(22), variable dead weights(27) and guides(23) for guide rods(6) being placed above the yoke assembly(8) such that the yoke lifts the bridge, the said bridge being provided with a hook(24) at its top for removably fixing to a release mechanism(25,26) fixed to the top bracing(3) of the said frame(l), a concrete feeder(ll) operated on a split two part twin track(28) being placed along the top face of the said mould block (7) in such a manner so as to allow free up and down movement of the mould block (7) containing block cast (14) on pallet(30) placed in between the bottom of said mould block and the top of the said horizontal platform(5). In an embodiment of the present invention the said yoke and bridge may be provided with a retaining/holding mechanism(31 to 41) so as to help ejection of the cast block (14) from the mould cavity(7a). For operating the machine for casting of blocks, the pallets(30) are first placed on the platform(5). For casting two blocks at a time, Two pallets(30) are placed side by side so that each comes right below the mould block (7) forming base of the mould cavity(7a). Measured quantity of concrete for one block is filled in each separate cavity of the trolley feeder(11). The feeder(11) is made to move to fill concrete in the mould cavity (7a) . Afterwards the bridge hook(24) is disengaged from the release pin(25) which allows the bridge(9) to fall down freely resulting in giving a blow through the plungers(22) on the concrete filled in mould cavity(7a). The form vibrators(13) are then started. Due to consolidation and settling of the concrete mass the bridge(9) keeps on descending until the full height blocks(14) are formed and the form vibrators(13) are then stopped. The mould block(7) is lifted up by operating the winch(lO). The cast block (14) are ejected on the pallets(30) which alongwith the blocks(14) are pulled out manually and taken away from the machine to curing yard. The mould block (7) is again brought down to rest on the platform(5) and the machine is thus again ready for next casting. When larger area of cast blocks comes in contact with the mould cavity(7a) (as in case of hollow blocks where due to the presence of cores attached with mould the area of contact increases), the cast hollow blocks(14) are likely to get lifted up with the mould block(7) during ejection thus making the operation of ejection of blocks(14) ineffective. This may also result in the breakage of the blocks (14) . To over come this, a retaining system has been developed and incorporated with the blockmaker to ensure positive locking of the bridge(9) particularly in a position which refers to the situation when full height of the cast blocks(14) has been achieved after the compaction in the mould cavity(7a). The retaining system comprises of a double wedge fork(31), a pin(33) which at one end is rigidly connected with the double wedge fork(31), and its other end is housed inside a sleeve(32) where the said pin(33) is retained in the sleeve(32) with the help of a cover(34), bolted at one end of the sleeve(32) and another cover(34) bolted at other end of the sleeve(32). The pin(33) carries a compression spring(35) which can be compressed in the sleeve(32) with the help of collar whenever the double-wedge fork(31), moves towards right. A pin(36) is attached at its one end with the double wedge fork (31) while the other end of the pin(36) is accommodated in a sleeve guide(37) which is welded with the sleeve(32). This arrangement does not allow the rotation of the assembly of double-wedge fork(31) with respect to the sleeve(32). The sleeve(32) has a rigidly connected base plate(38) to help bolting of the sleeve(32) with a cross member of channel section(39) which forms a rigid connection between the said two pillars(2). A wedge(40) is connected with each of the aforesaid two bridge guides(23).. Another wedge(41) is connected with each of the two yoke guides (8) . After the concrete is filled in the moulds (7a), the bridge (9) is allowed to drop freely to give an impact force through the plunger(22) on the concrete filled in the moulds (7a) . As the concrete is vibrated with the help of vibrators(13), it settles down in the mould(7a) thus allowing the plungers(22) and bridge(9) to come down further. While coming down, the bridge(9) establishes contact with the double wedge fork(31) through the wedge(40) and pushes the former inside the sleeve(32) until the wedge (40) fits inside the central recess of double wedge fork(31) thus stopping further going down of the bridge(9). This is the position when full height blocks(14) have been formed in the mould (7a) . In situations when the blocks (14) also get lifted up alongwith the moulds(7a) due to larger frictional force, the positive locking of the bridge(9) through the wedge(40) and double-wedge fork(31) does not allow the blocks(14) to move up with the mould(7a). During hoisting when the bottom edge of the mould(7a) clears the top face of the cast block(14), the top slant edge of the wedge(40) comes in contact with lower slant edge of the double wedge fork(31). On further hoisting, the double wedge fork(40) is pushed inside the sleeve(32) thus disengaging the wedge(40) from the double wedge fork(31). This is the position when on further hoisting of the yoke assembly(8), the plungers(22) also leave contact from the cast blocks(14) and are lifted above them allowing the blocks(14) to be taken out of the machine. As the yoke assembly (8) is hoisted up further, the vertical face of the wedge(41) keeps the double wedge fork(31) pressed towards right and maintain the later in that position till full length of the vertical face of wedge(41) is cleared of the double wedge fork(31). On further hoisting of the yoke (8), the bridge (9) can be hanged with the roller pin(25). During the free fall of the bridge(9) from this position, the slant lower edge of wedge (40) first comes in contact with the double widge fork (31) and gets clear of it by pushing the double wedge fork(31) inside the the sleeve(32). Measured quantity of concrete is fed into the mould(7a) with the help of a concrete feeder comprising of a trolley feeder(11) which has four wheels which move on two separate tracks(28) and wherein the trolley feeder(11) has two separate cavities each meant to house concrete for filling two separate cavities of the mould(7a), an electric motor which powers a speed reducer which carries a sprocket on its output shaft. The sprocket is connected through a cha in with another sprocket which carries a pinion mounted on its shaft. The pinion meshes with a rack which is centrally placed on and rigidly connected to a feeder platform. The assembly of electric motor, speed reducer, sprockets and the pinion are all mounted on a trolley which moves on its four wheels on the aforesaid tracks(28). The trolley is connected with the trolley feeder(11) through a connector. Another track is laid and connected with the top face of the aforesaid mould. Both the tracks are kept in line and in level with each other but are separated with a minute gap(29). The inward and outward movements of the trolley feeder(11) are controlled with two separate switches. The main advantages of the present invention are : (i) This is the only block making device developed for the first time which is suitable for handling lean concrete mixes of low mobility for making economical concrete blocks and other products using larger aggregates, around 50mm and ensures uniformity in dimensions and density and consequently in strength. (ii) The invented device has applications wherever making blocks on site is easy and cheaper and may help in avoiding delays and transportation damages. (iii) The invented device is light, compact and is easily transported from one location to another at the site. While working, the device needs no anchorage with the ground. This feature makes the invented device highly suitable for hilly regions of the country where concrete block is a potential alternative to the fired clay brick. (iv) The device is so designed that after little training, semi-skilled labour can easily run and maintain it. This increases its suitability for rural areas also besides the urban sectors. (v) Besides being suitable of making large aggregate solid concrete blocks, the invented device is capable of making hollow concrete blocks and all other products which are made on the available block making machines. (vi) It is possible to vary the amplitude of vibration by making adjustment in the eccentric weights of the vibrator. With a judicious selection of top pressure on the concrete and the amplitude of vibration, concrete mixes of flowable to stiff consistency can be easily handled on the invented device. (vii) A concrete feeder has been used on the device to feed measured quantity of concrete in the mould. The feeder can be operated manually or by power. Screeding of concrete in the mould has been altogether eliminated. This feature has drastically reduced the cycle time and problems associated with the handling and leveling of large aggregates in the concrete and has finally resulted in increased productivity. (viii) By using different moulds and matching plungers, blocks and other products of various shapes and sizes are easily cast on this device. We claim : 1. A device useful as a concrete block maker which comprises a frame(1) consisting of a plurality of vertical pillars(2) having top and bottom cross bracings(3,4), a horizontal platform(5) rigidly fixed to the said frame(1) at appropriate height, a plurality of vertical guide rods(6) being fixed between the top (3) and bottom(4) bracings along two opposite sides of said frame(1), a yoke assembly(8) having a plurality of guides being placed in such a manner so as to slide along the aforesaid vertical guide rods(6), the yoke assembly capable of being lifted/ lowered by means (10,20,21), the yoke assembly(8) being connected to mould frame(12) through a plurality of lifting pins(15) by means(16,17,18,19), a mould block(7) having a plurality of mould cavity(7a) to hold concrete block(14) being rigidly fixed with the said mould frame(12) which skirts around the mould block(7), the said mould frame(12) being provided with atleast two form vibrators(13), a bridge(9) having a plurality of vertical plungers(22), variable dead weights(27) and guides(23) for guide rods(6) being placed above the yoke assembly(8) such that the yoke lifts the bridge, the said bridge being provided with a hook (24) at its top for removably fixing to a release mechanism(25,26) fixed to the top bracing(3) of the said frame(1), a concrete feeder(11) operated on a split two part(28,29) twin track(28) being placed along the top face of the said mould block (7) in such a manner so as to allow free up and down movement of the mould block(7) containing block cast(14) on pallet (30) placed in between the bottom of said mould block and the top of the said horizontal platform(5). 2. A device as claimed in Claim 1 wherein the yoke and bridge are provided with a retaining/holding mechanism(31 to 41), such as herein described, so as to help ejection of cast block(14) from the mould cavity(7a). 3. A device useful as a concrete block maker substantially as herein described with reference to Figs. 1 to 4 of the drawings accompanying this specification.

Documents:

2268-del-1997-abstract.pdf

2268-del-1997-claims.pdf

2268-del-1997-complete specification (granted).pdf

2268-del-1997-correspondence-others.pdf

2268-DEL-1997-Correspondence-PO.pdf

2268-del-1997-description (complete).pdf

2268-del-1997-form-1.pdf

2268-del-1997-form-19.pdf

2268-del-1997-form-2.pdf

2268-del-1997-gpa.pdf