Process of and apparatus for forming concrete pipe with step

Abstract

 A pallet (15) is connected to a lower end of an outer mold jacket (13) and a core segment (8) to which a step member (27) is attached is removably attached to the pallet (15), and then stiff consistency concrete material is thrown into a forming spacing (19) defined between an inner mold core (1) and the outer mold jacket (13) and is then compacted, whereafter the outer mold jacket (13) and the pallet (15) are lifted to remove a thus formed concrete pipe, and then the core segment (8) is removed from the pallet (15) to separate the same from the step member (27).
With the process, an attaching operation of the step member to the core segment and a separating operation of the core segment from the step member after removal of the product can be performed outside the inner mold core. Further, the step member can be retained by the core segment at a location at which it is to be attached until the formed concrete pipe is hardened thoroughly.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] This invention relates to a concrete pipe forming process and apparatus wherein a concrete pipe which is used for a manhole and so forth is formed while a step member is simultaneously fixed to the concrete pipe.

2. Description of the Prior Art

[0002] A concrete pipe forming apparatus is already known and disclosed, for example, in European Patent No. 0160170 which includes a movable outer mold jacket, a hollow inner mold core disposed at a fixed position, and a core segment adapted to fit in a recess of the inner mold core to complete a forming profile and mounted for movement into and out of the inner mold core in such a manner as to open or close the recess of the inner mold core from the inside of the inner mold core. A plurality of slits are formed in the core segment for individually holding a plurality of step members therein. In molding, the outer mold jacket is retracted to a position above the inner mold core and the recess of the inner mold core is closed with the core segment, and then the step members are inserted into the slits of the core segment from the outside of the inner mold core and then locked there, whereafter the outer mold jacket is moved down until a forming spacing is defined between the outer mold jacket and the inner mold core. After then, stiff consistency concrete material is thrown into the forming spacing while applying vibrations to the inner mold core to compact the concrete material. Upon removal, the step members are unlocked and the core segment is retracted inwardly of the inner mold core to release the step members therefrom, and then the outer mold jacket is moved up, whereafter a concrete article (concrete pipe) in a semi-hardened condition is lifted together with a ring-shaped pallet to remove the same from the forming spacing and is moved to a curing location.

[0003] With the conventional method, however, since the step members must be attached from the outside of the inner mold core to the core segment mounted in the inner mold core, the operability is very low, and this is particularly true when the working is performed in a vertical shaft under the ground. Further, since the core segment is retracted inwardly of the inner mold core to separate the core segment from the step members when the concrete article is to be removed, the stem members released from the core segment upon such retracting movement of the core segment or upon removal or movement to a curing location of the article are sometimes suspended or loosened or, in an extreme case, come off from the concrete article which is not yet in a completely hardened condition.

SUMMARY OF THE INVENTION

[0004] It is an object of the present invention to provide a concrete pipe forming process and apparatus wherein an attaching operation of a step member to a core segment and a separating operation of the step member from the core segment after removal of a formed concrete pipe can be performed outside an inner mold core to improve the operability.

[0005] It is another object of the present invention to provide a concrete pipe forming process and apparatus wherein a step member can be kept retained by a core segment at a location at which it is to be attached until a formed concrete pipe is hardened thoroughly.

[0006] In order to attain the objects, according to the present invention, there is provided a concrete pipe forming process wherein, using an inner mold core placed at a fixed location, a core segment adapted to be received in a recess of the inner mold core to complete a forming profile of the inner mold core, a ring-shaped pallet adapted to removably fit on an outer periphery of the inner mold core and a movable outer mold jacket, a step member is attached to the core segment and stiff consistency concrete material is thrown into a forming spacing defined between the inner mold core and the outer mold jacket, and then the inner mold core is vibrated to compact the concrete material, whereafter the outer mold jacket is lifted to lift a thus formed concrete pipe together with the pallet to remove the concrete pipe from the inner mold core, which is characterized in that the pallet is connected to a lower end of the outer mold jacket and the core segment is removably attached to the pallet, and then stiff consistency concrete material is thrown into the molding spacing and compacted, whereafter the outer mold jacket and the pallet are lifted to remove the concrete article from the inner mold core, and then the core segment is removed from the pallet to separate the same from the step member.

[0007] With the forming process, since the core segment can be separated from the inner mold core and the step member can be attached to the core segment at a suitable location outside the inner mold core, the operability is high. Further, while the step member is kept retained by the core segment, the formed concrete pipe can be removed from the inner mold core and simultaneously the core segment can be separated from the inner mold core. Then, after the pallet is separated from the outer mold jacket and the concrete pipe is moved to a curing location together with the pallet, the core segment can be removed from the pallet to cancel such retention of the step member by the core segment. Consequently, possible play or coming off of the step member can be prevented by the core segment until after the concrete pipe is hardened thoroughly.

[0008] Preferably, the inner mold core is disposed in a vertical shaft under the ground and the compacting operation of the concrete material is performed in the vertical shaft in order to prevent noises caused by vibrations, and attachment and removal of the stem member to and from the core segment, attachment and removal of the core segment to and from the pallet and removal of the formed concrete pipe from the outer mold jacket and the core segment are performed on the ground to assure a high operability.

[0009] The step member may be locked with respect to the core segment so that the step member may not move inadvertently during formation of the concrete pipe, and after removal of the formed concrete pipe from the outer mold jacket, the step member may be released from the core segment to separate them from each other.

[0010] Preferably, the core segment is fitted into the recess of and closely contacted with the inner mold core before concrete material is thrown into the forming spacing so that vibrations from the inner mold core may be transmitted with certainty to the core segment during compacting operation by vibrations of the concrete material, and after formation of the concrete pipe, the core segment is released from the inner mold core to remove the formed concrete pipe.

[0011] Preferably, a cover plate is mounted, when the step member is received in a slit formed in the core segment to retain the same on the step member, on the step member so that concrete material may not leak through a gap defined between the step member and the core segment in the slit.

[0012] The above and other objects, features and advantages of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] 

FIG. 1 is a plan view of a concrete pipe forming apparatus in a forming condition showing a preferred embodiment of the present invention;

FIG. 2 is a sectional view taken along line X-X of FIG. 1;

FIG. 3 is an enlarged view of part of FIG. 2;

FIG. 4 is an enlarged rear elevational view of the part shown in FIG. 3;

FIGS. 5(1) to 5(8) are schematic sectional views showing different steps of an assembling procedure of the forming apparatus of FIG. 1 to a forming condition and also of a forming procedure;

FIG. 6 is a perspective view showing a modified core segment; and

FIG. 7 is a sectional view of part of a forming apparatus in which the core segment of FIG. 6 is incorporated.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0014] Referring first to FIGS. 1 and 2, there is shown a concrete pipe forming apparatus to which the present invention is applied. The forming apparatus shown includes a cylindrical inner mold core 1 having a closed top end and mounted vertically on a base plate a in a vertical shaft 2 under the ground. Also a vibrator 4 is mounted on the base plate 3 in the inner mold core 1. The vibrator 4 vibrates when rotation of a motor 5 is transmitted thereto by way of a belt 6, and such vibrations are transmitted to the inner mold core 1 by way of a plurality of connecting members 7. A recess 9 for receiving a core segment 8 therein is formed at part of an outer circumferential wall of the inner mold core 1 and extends from the top to the bottom end of the inner mold core 1. When the core segment 8 is fitted in the recess 9, an arcuate outer face thereof interconnects an outer circumferential face of the inner mold core 1 into a circular shape to complete a circular forming profile of the inner mold core 1. The base plate 3 is disposed horizontally on a base frame 11 by way of a plurality of vibration insulating members 10 for damping vibrations. An opening of the vertical shaft 2 is closed with a lid plate 12 in order to prevent noises.

[0015] Meanwhile, an outer mold jacket 13 is constructed for free movement, that is, is not located at a fixed position and may be inserted into the vertical shaft 2 through an opening 14 of the lid plate 12 by means of a crane or the like. A ring-shaped pallet 15 is removably attached to a lower end of the outer mold jacket 13 by known means. When the outer mold jacket 13 is inserted into the vertical shaft 2, the pallet 15 is removably fitted around an outer periphery of the inner mold core 1 with a predetermined fixed gap left between the inner mold core 1 and the outer mold jacket 13. A receiving seat 16 for receiving the pallet 15 thereon is provided at a lower portion of the outer periphery of the inner mold core 1, and when the pallet 15 is fitted onto the inner mold core 1 until it is received by the receiving seat 16, a flange 17 provided at the top end of the outer mold jacket 13 is received on the lid plate 12 with a plurality of vibration isolating members 18 interposed therebetween to hold the outer mold jacket 13 at a predetermined height or vertical position. Where the outer mold jacket 13 is set in such position, a forming spacing 19 which is closed at the bottom end thereof with the pallet 15 is defined between the inner mold core 1 and the outer mold jacket 13.

[0016] The core segment 8 is removably attached to the pallet 15, and as the pallet 15 is fitted around the outer periphery of the inner mold core 1, the core segment 8 is fitted simultaneously into the recpss 9 of the inner mold core 1. Such fitting condition and an attaching condition of the core segment 8 are shown in detail in FIGS. 3 and 4. Referring also to FIGS. 3 and 4, the pallet 15 has a cutaway portion 20 formed therein in which the bottom end of the core segment 8 can be fitted. A vertical flange 21 is formed integrally on a lower face of the pallet 15 and has a pair of brackets 22 formed therein in the region of the recess 20, and a pair of projections 24 each having a pin 23 thereon are provided on opposing faces of the brackets 22. Meanwhile, another bracket 25 is provided on the lower face of the core segment 8 and has a pair of small holes 26 formed therein in which the pins 23 can be fitted. The core segment 8 is attached in a vertically erected condition to the pallet 15 by fitting the lower end thereof in the recess 20 of the pallet 15 and fitting the pins 23 in the small holes 26. Such attaching is performed before the outer mold jacket 13 is set in position as described above and besides before the pallet 15 is attached to the outer mold jacket 13.

[0017] It is to be noted that the core segment 8 can be retained on the pallet 15 using a magnet. Preferably, seal members are provided along a circumferential edge of the recess 20, between the pallet 15 and the,outer mold jacket 13 and between the core segment 8 and the recess 9 of the inner mold core 1 so that concrete material filled in the molding spacing 19 may not leak.

[0018] The core segment 8 is formed as a box which is closed at the top and bottom, the opposite left- and right-hand sides and the front side thereof and is open at the rear side thereof, and a pair of upper and lower horizontally elongated slits 28 for receiving step members 27 therein are formed in the front wall of the core segment 8 which has an arcuate shape in plan. A tubular guide projection 29 is formed around a circumferential edge of each of the slits 28 such that it extends into the core segment 8.

[0019] Each of the step members 27 is formed from a metal bar and has a straight foot hold portion 30, a pair of left and right arms 31 and hooked portions 32 provided at ends of the arms 31. Each of the foot hold portions 30 and the left and right arms 31 of the step members 27 is partly covered with a plastic material. A horizontally elongated cover plate 33 made of a plastic material is securely fixed between the left and right arms 31 of each of the step members 27. The cover plates 33 are provided to close the slits 28 in the core segment 8 so that concrete material filled in the forming spacing 19 may not leak through the slits 28, and are curved in accordance with an arc of the front face of the core segment 8. Each of the cover plates 33 has a pair of holes 34 formed therein through which the left and right arms 31 of the cover plate 33 extend and further has a projection 35 formed therein which is fitted in the slit 28.

[0020] The step members 27 extend through the slits 28 such that the hooked portions 32 thereof are projected forwardly from the core segment 8 while the foot hold portions 30 thereof are located inwardly of the core segment 8. A locking device for locking the step members 27 received in the slits 28 is provided inwardly of the core segment 8. The locking device has the following construction. In particular, a projection or wide rib 36 is formed on the core segment 8 and extends vertically between the upper and lower guide projections 29, and a locking plate 37 is supported for pivotal motion on the projection 36 by means of a fastening screw 38 with a knob. The locking plate 37 has a pair of tapered portions 38 formed at upper and lower end portions thereof such that it is decreased in thickness toward the ends thereof. Thus, if the step members 27 are fitted into the upper and lower slits 28 and the upper and lower tapered portions 39 of the locking plate 37 are compulsorily inserted between the foot hold portions 30 of the step members 27 and the guide projections 29 and then the fastening screw 38 is tightened to fasten the locking plate 37 to prevent pivotal motion of the locking plate 37, the step members 27 are locked with respect to the core segment 8 while they are received in the slits 28. It is to be noted that such locking may alternatively be achieved indirectly making use of the cover plate 33.

[0021] If the core segment 8 to which the step members 27 are attached in such a manner as described above is fitted into the recess 9 of the inner mold core 1 and the outer mold jacket 13 are set in position, then only the hooked portions 32 of the step members 27 are positioned in the forming spacing 19.

[0022] Subsequently, a procedure until such forming apparatus is assembled to such a condition as described above and a forming procedure with the forming apparatus will be described with reference to FIGS. 5(1) to 5(8).

[0023] First, the core segment 8 is either erected uprightly on a floor on the ground or laid horizontally such that the arcuate front face thereof is directed upwardly, and then the step members 27 are fitted into the two slits 28 of the core segment 8 and then locked by means of the locking plate 37 in such a manner as described above. Then, a lower end of the core segment 8 to which the step members 27 are attached in this manner is fitted into the recess 20 of the pallet 15 to attach the core segment 8 to the pallet 15 in such en uprightly erected condition as seen in FIG. 5(1). It is to be noted that alternatively the step members 27 may be attached to the core segment 8 after the core segment 8 is attached to the pallet 15.

[0024] Subsequently, a reinforcement 40 in the form of a cylindrical cage or basket is set in position on the ground as shown in FIG. 5(2), and the outer mold jacket 13 is disposed on the outer side of the reinforcement 40 and a lower end of the outer mold jacket 13 is connected to the pallet 15. After then, the outer mold jacket 13 is lifted using a crane or the like making use of the flange 17 of the outer mold jacket 13 and is fitted into the vertical shaft 2 until the pallet 15 is fitted on the outer periphery of the inner mold core 1 and the core segment 8 is fitted into the recess 9 of the inner mold core 1 to set the outer mold jacket 13 in position as shown in FIG. 5(3). Simultaneously, the reinforcement 40 is disposed in position into the forming spacing 19.

[0025] In this condition, stiff consistency concrete material 41 is thrown into the forming spacing 19 as seen in FIG. 5(4) while vibrations are applied to the inner mold core 1 by means of the vibrator 4 to compact the concrete material 41, and then an upper face of the thus filled concrete material 41 is pressed into a leveled condition by a press member 42, whereafter application of vibrations is stopped. Consequently, a concrete pipe is formed which is not yet hardened thoroughly with the reinforcement 40 and the hooked portions 32 of the step members 27 embedded therein.

[0026] Then, the flange 17 of the outer mold jacket 13 is grasped by a grasping member 43 to lift the outer mold jacket 13 as shown in FIG. 5(5) while the pallet 15 and the core segment 8 are separated from the inner mold core 1. Consequently, the thus formed concrete pipe 44 is removed from the inner mold core 1. Then, the concrete pipe 44 is moved to a curing location together with the outer mold jacket 13 as shown in FIG. 5(6) and the outer mold jacket 13 is disconnected from the pallet 15, and then the outer mold jacket 13 is lifted to separate the same from the concrete pipe 44 as shown in FIG. 5(7). Immediately after then or after it is waited after then that a hardened condition of the concrete is stabilized, the step members 27 are released from the locking plate 37, and the core segment 8 is removed from the recess 9 of the inner mold core 1. Consequently, the concrete pipe 44 is obtained in which the reinforcement 40 and the hooked portions 32 of the step members 27 are embedded while the foot hold portions 30 of the step members 27 are projected inwardly from an inner face thereof as shown in FIG. 5(8). The concrete pipe 44 is left placed on the pallet 15 to cure for a predetermined period of time, and then it is removed from the pallet 15 and used as a product.

[0027] During operation from the step of FIG. 5(2) to the step of FIG. 5(5), such assembling step as shown in FIG. 5(1) can be performed with another pallet and another core segment. Further, the outer mold jacket 13 and the pallet 15 may be set to predetermined different positions from each other and/or removed separately from each other. In this instance, the outer mold jacket is first lifted, and then the pallet is lifted to remove the formed concrete pipe from the same.

[0028] Referring now to FIG. 6, there is shown a modification to the core segment 8. The modified core segment 45 additionally includes a pair of upped and lower bearing members 46 securely mounted on an inner face thereof just below the upper and lower slits 28, respectively, and a hook 47 is mounted for pivotal motion on each of the bearing members 46 by means of a pin 48. The hooks 47 are disposed for engagement with the foot hold portions 30 of the step members 27 to retain the step members 27 fitted in the slits 28 of the core segment 45. Preferably, each of the hooks 47 is constituted such that a lower portion thereof has a greater weight than an upper portion thereof such that the center of gravity thereof is positioned lower than the center of pivotal motion thereof so that engagement thereof with the foot hold portion 30 may be kept by moment of the hook 47 which is caused by such location of the center of gravity. A horizontal plate 49 is further provided integrally on the inner face of the core segment 45, and a pair of left and right brackets 50 are securely mounted on the lower end of the core segment 45. The horizontal plate 49 has a recess 51 formed at the center of an inner end portion thereof and has a pair of holes 52 formed therein on the opposite sides of the recess 51. Each of the left and right brackets 50 has a fitting groove 53 defined by a pair of upper and lower ribs thereon. The opposite left and right end edges of a projection 54 formed on an inner periphery of the pallet 15 can be fitted into the fitting grooves 53 of the left end right brackets 50 in order to attach the core segment 45 to the pallet 15.

[0029] Referring now to FIG. 7, there is shown part of a concrete pipe forming apparatus assembled in a forming condition employing the modified core segment 45. In the forming apparatus which employs the core segment 45, a vertically elongated guide plate 55 is provided at the center of the recess 9 of the inner mold core 1 while a locking cylinder device 56 is disposed in the inner mold core 1. The cylinder device 56 has a piston rod 57 which extends through a hole 56 formed in the inner mold core 1 into the recess 9. A pair of pawls 59 for fitting into the holes 52 formed in the horizontal plate 49 of the core segment 45 are mounted at end portions of the piston rod 57.

[0030] In order to reach the condition shown in FIG. 7, the core segment 45 is attached to the pallet 15 with the left and right fitting grooves 53 thereof fitted with the left and right end edges of the projection 54 of the pallet 15, and then the pallet 15 is connected to the lower end of the outer mold jacket 13, whereafter the pallet 15 is fitted around the outer periphe,ry of the inner mold core 1 and the core segment 45 is fitted into the recess 9 of the inner mold core 1 while the recess 51 of the horizontal plate 15 is fitted with the guide plate 45, and in this condition, the outer mold jacket 13 is moved down. During such downward movement, the hooks 47 are slidably engaged with the guide plate 55 to retain the foot hold portions 30 of the step members 27 thereon. When the outer mold jacket 13 is set in position, the pawls 59 on the piston rod 57 of the cylinder device 56 are fitted into the holes 52 of the core segment 45. Thus, if the cylinder device 56 is operated to retract the piston rod 57, the core segment 45 is fitted closely into the recess 9 while the hooks 47 are pushed by the guide plate 55 so that they are closely contacted with the foot hold portions 30 of the step members 27 thereby to lock the step members 27. In this condition, the liquid-tight condition between the core segment 45 and the inner mold core 1 is maintained and vibrations of the inner mold core 1 are transmitted to the core segment 45 with certainty, and besides, possible play of the step members 27 with respect to the core segment 45 is prevented with certainty.

[0031] When a concrete pipe formed by the forming apparatus is to be removed, the cylinder 56 is rendered inoperative to allow advancing movement of the piston rod 57, and then the core segment 45 and the pallet 15 are lifted together with the outer mold jacket 13. Upon such lifting movement, the pawls 59 on the piston rod 57 are brought out of engagement with the holes 52 of the horizontal plate 49 of the core segment 45 while the core segment 45 is pulled up away from the recess 9 of the inner mold core 1 along the guide plate 55. Since the hooks 47 on the core segment 45 still remain in engagement with the step members 27 even after the formed concrete pipe is removed, possible play of the steps 27 is prevented by the hooks 47. In order to separate the core segment 45 from the formed concrete pipe and the pallet 15, the hooks 47 are first pivoted to disengage from the step members 27, and then the core segment 45 is pulled horizontally along the left and right end edges of the projection 54 of the pallet 15.

Claims

1. A concrete pipe forming process wherein, using an inner mold core placed at a fixed location, a core segment adapted to be received in a recess of said inner mold core to complete a forming profile of said inner mold core, a ring-shaped pallet adapted to removably fit on an outer periphery of said inner mold core and a movable outer mold jacket, a step member is attached to said core segment and stiff consistency concrete material is thrown into a forming spacing defined between said inner mold core and said outer mold jacket, and then said inner mold core is vibrated to compact the concrete material, whereafter said outer mold jacket is lifted to lift a thus formed concrete pipe together with said pallet to remove the concrete pipe from said inner mold core, characterized in that said pallet is connected to a lower end of said outer mold jacket and said core segment is removably attached to said pallet, and then stiff consistency concrete material is thrown into said molding spacing and compacted, whereafter said outer mold jacket and said pallet are lifted to remove the concrete article from said inner mold core, and then said core segment is removed from said pallet to separate the same from said step member.

2. A concrete pipe forming process as set forth in claim 1, characterized in that said inner mold core is disposed in a vertical shaft under the ground and the compacting operation of the concrete material is performed in said vertical shaft, but attachment and removal of said stem member to and from said core segment, attachment and removal of said core segment to and from said pallet and removal of the formed concrete pipe from said outer mold jacket and said core segment are performed on the ground.

3. A concrete pipe forming process as set forth in if claim 2, characterized in that said step member is locked with respect to said core segment during formation of the concrete pipe, and after removal of the formed concrete pipe from said outer mold jacket, said step member is released from said core segment to separate them from each other.

4. A concrete pipe forming process as set forth in claim 1, characterized in that said core segment is fitted into said recess of and closely contacted with said inner mold core before concrete material is thrown into said forming spacing, and after formation of the concrete pipe, said core segment is released from said inner mold core to remove the formed concrete pipe.

5 A concrete pipe forming process as set forth in claim 1, characterized in that the concrete material is compacted in a condition wherein said step member is received in a slit formed in said core segment and said slit is covered with a cover plate mounted on said step member.

6. A concrete pipe forming apparatus which includes an inner mold core placed at a fixed location, a core segment adapted to be received in a recess of said inner mold core to complete a forming profile of said inner mold core, a ring-shaped pallet adapted to removably fit on an outer periphery of said inner mold core, a vibrator disposed in said inner mold core, and a movable outer mold jacket and wherein a step member is attached to said core segment and stiff consistency concrete material is thrown into a forming spacing defined between said inner mold core and said outer mold jacket, and then said inner mold core is vibrated to compact the concrete material, whereafter said outer mold jacket is lifted to lift a thus formed concrete pipe together with said pallet to remove the concrete pipe from said inner mold core, characterized in that said recess is formed in an outer periphery of said inner mold core, that said pallet includes means for removably retaining said core segment thereon, and that said core segment is fitted from an upper end into said recess when said pallet is fitted around said inner mold core.

7. A concrete pipe forming apparatus as set forth in claim 6, characterized in that said core segment has a slit formed therein such that said step member may be received therein, and said core segment further has a locking device provided thereon for locking said step member fitted in said slit.

8. A concrete pipe forming apparatus as set forth in claim 7, characterized in that said locking device includes a pivotal hook for engaging with a foot hold portion of said step member.

9. A concrete pipe forming apparatus as set forth in claim 6, characterized in that said inner mold core includes means for causing said core segment received in said recess to be closely contacted with said inner mold core.

Drawing