US 1932150 A
Description (OCR text may contain errors)
Patented Get. 24, 1933 1,932,150 I I METHOD or Maxine. CEMENTITIOUSPIPE Manabu Tada, Tokyo, Japan, assignor to Frank W. Plane, Chicago, Ill.
No Drawing. Application JanuaryS, 1932 Serial No. 585,640 I 4 Claims. (01. 25-454) This invention relates to improvements in method of making cementitious pipe.
In the making of cement pipe according to ordinary and well known processes, it is custom- 5 ary to mold or form the pipe upon a core or mandrel while the cement is in a plastic condition, and thereafter to allow the cement to dry and harden upon the core until the cement has become thoroughly set throughout, after which the core is removed from the interior and the pipe section allowed to become thoroughly cured and hardened before use. This method of making pipe is open to the objection that it requires a complete hardening of the pipe throughout before the core is removed, which necessarily ties up the use of the cores for a considerable period of time, and at the same time involves difiiculty in the removal of the cores from the thoroughly hardened pipe sections.
In the making of pipe by the common process, it is notfeasible to remove the core at an early stage in the drying and hardening operation and while the'cement or other cementitious material is in a plastic condition, since an attempt to rei move the core at this stage would usually result in a deformation of the pipe either during or after the removal of the core.
The present invention is designed to overcom the difficulties noted by subjecting the pipe sec tions, while on the forms or cores, to a drying or surface hardening in an atmosphere of carbon dioxide (00 which has the effect, by chemical reaction, of rapidly hardening the surface of the pipe to a degree suilicient to prevent deformation and to allow the core to be thereafter removed while the interior surrounding the core is in a more or less plastic condition, so that the removal of the core will be facilitated, thereby making the core available for further use while the pipe 9 sections are gradually drying out and setting, and obviating the necessity for completely hard ening the pipe sections before the cores are again available for use.
The present invention is particularly directed to the manufacture of asbestos cement pipes,
wherein a pipe composed of a mixture of a..- bestos fibres and a suitable cementitious binder is formed upon the core and dried in a drying chamber supplied with heated gas containing CO2 until the outer portions only of the pipe are dried and stiffened, the inner portions remaining moist and flexible, after which the core is removed and the drying continued under normal atmospheric conditions. Although the nature of the chemical surface reaction which occurs when the plastic cementive composition is subjected to CO: is not thoroughly understood, it has beenfound that when cement is mixed with water and reacts with 00 ,1 obtain COBCa (calcium carbonate), which furnishes a very hard and quickly formed outer shell or hardened surfacefor the pipe section, which permits the form or core to be removed from the still plastic interior of the pipe section without tending to disrupt or deform the section either during the removal of the core or thereafter. By thus-preliminarily case hardening the pipe sections in an atmospher'eof 002, the sections can be sufficiently hardened, in a very short space of time, to permit removal from the drying charn- 70, ber, after which the cores can themselves be removed and again used while the previously formed pipe sections are stacked up and allowed to thoroughly dry and harden throughout a sufficient period of time to condition them for use. i
In making pipe in conformity with the present method, it is not necessary to use any special form of drying chamber or conveyor for the pipe sections, since the case hardening operation may be performed in any closed room or receptacle into which the pipe sections may be introduced continuously or in batches, and subjected to the hardening operation for a sufficient period of time to secure an initial hardening sufficient in v degree to permit the removal of the pipe sections from the cores without deformation. The particular length of time required will depend to some extent upon the character of the cementitious mixture employed and the diameter and thickness of the pipe sections and the facilities available for the removal of the cores, but in all cases it is sufiicient only to allow them to remain in the CO2 atmosphere for a suflicient period of time to secure the necessary hardening required to facilitate the subsequent manipulation of the pipe sections and permit them to be stacked or stored for final hardening.
Pipe sections manufactured in accordance with the present method, when composed of asbestos fibres and cement, will possess a close, firm texture and relatively great strength, and at the same time they will readily withstand the deleterious effects of gases or chemicals which frequently attack pipe manufactured wholly of cee 1,05 ment in the ordinary way.
The pipe manufactured in accordance with the present invention is peculiarly suitable for use in fiues or conduits for the passage of smoke or gaseaand in fact is useful under all conditions in which similar piping is customarily employed, as well as under certain conditions which have heretofore precluded the use of ordinary cement pipe.
Although the method of the present invention has been described as applicable to the manufacture of pipe sections, it is not the intention, unless otherwise indicated in the claims, to limit the invention to the making of pipes, since other products formed of cementitious material molded to shape while in the plastic state may be advantageously hardened in the manner described and irrespective of the particular configuration of the products so treated.
1. The method of hardening a cementitious product, which consists in subjecting the same while in a plastic state to an atmosphere containing CO2 in order to effect a quick surface hardening of the same sufiicient to render the product self-sustaining, and in thereafter removing said product from said atmosphere while the interior portion remains soft and allowing the same to completely harden under normal atmospheric conditions.
2. The method of hardening a cementitious product, which consists in the forming of such a product on a core while in the plastic state and subjecting said product upon the core to an atmosphere containing CO2 in order to effect a surface hardening thereof sufficient to render the product self-sustaining prior to the removal of said product from the core, and in thereafter removing said product from the core while the interior surfaces contiguous to the core are still in a soft enough condition to permit easy removal of the core.
3. The method of hardening a cementitious product, which consists in the forming of such a product on a core while in the plastic state and subjecting said product upon the core to an atmosphere containing CO2 in order to effect a surface hardening thereof suflicient to render the product self-sustaining priorto the removal of said product from the core, and in thereafter removing said product while mounted upon the core from the atmosphere containing CO2, removing the product from the core while the interior surface contiguous to the core is still in a relatively softoondition, and continuing the drying and hardening of the product under normal atmospheric conditions.
4. The method of hardening a cementitious pipe section, which consists in forming said pipe section while in a plastic state upon a core, and subjecting the pipe section while in a soft condition to an atmosphere containing CO2 to effect asurface hardening of the pipe section sufficient to render the product self-sustaining, and in removing the pipe section from said atmosphere and thereafter removing the core from the pipe section While the interior surface of said section contiguous to the core is still in a soft condition, and in continuing the hardening under normal atmospheric conditions.