Abstract:
As a part of the manufacture of concrete products, such as concrete pipe, manholes and the like, the joint rings applied during the casting process much be removed. The invention relates to a joint ring removal system in which a vertically oriented concrete product, containing a joint ring, is gripped to hold the product stationary while a joint ring pulling force is applied. Then, a shocking force is applied laterally to the joint ring to free it from the concrete joint. The amount of pulling force applied to the joint ring is less than that required to separate the joint ring from the concrete while the shocking force is applied in a direction transverse to the pulling force so that no harmful tensile shocking forces are transmitted to the concrete joint. The pulling force on the joint ring is variably applied and timed with the shocking force.

Description:
BACKGROUND OF INVENTION 
     This invention relates to machines and processes for manufacturing concrete products, such as concrete pipe, manholes, catch basins, and the like. During the manufacturing process, a joint-forming ring, of cast iron or steel, is pressed into the top of the concrete pipe or manhole segment. This joint ring remains in place during the curing of the concrete in order to ensure a high quality joint. After the concrete is cured, the joint ring must be removed from the concrete product in such a way that the concrete joint of the product is not damaged. 
     In some operations, the joint rings are removed manually by hammering on the ring and by the use of heavy hand and power tools which involve repetitive movements by the worker that can lead to work related physical conditions. Therefore, to provide protection against cumulative trauma disorder of workers, systems have been developed to automate the joint ring removal operation. In one system, the cured concrete segment is oriented vertically and one ring at a time is pulled from the end of the pipe. As a part of the automation of the joint ring removal, the rings are gripped by appropriate grippers and a shock force is applied vertically along the axis of the pipe to free the joint ring from the product while an axially pulling force is applied. With the known prior art apparatus of this type, it is not uncommon for the concrete joint to be damaged if the pulling force is not applied uniformly to the joint ring. Even so, it is not uncommon for the shocking force, which is applied axially, to cause breakage of the concrete joint. 
     In another prior art system disclosed in U.S. Pat. No. 5,587,185, the joint ring removal is accomplished while the concrete pipe is positioned horizontally and the joint rings are removed simultaneously from both ends of the pipe. Although this system is utilized in high production automated systems where multiple pipes are being transported along a horizontal conveyor, there is a need for a joint ring removal apparatus and method in production facilities where the concrete pipes are stored vertically for curing and are individually handled using automated robotics. The method and apparatus of the invention will satisfy this need by providing an apparatus and method for removing a joint ring from a cured finished product in a manner that will greatly minimize, if not eliminate, damage to the concrete joint. 
     SUMMARY OF INVENTION 
     The method and apparatus of the invention provides a joint ring removal system in which a vertically oriented concrete product containing a joint ring is gripped to hold the product stationary while the joint ring pulling force is applied, and then a shocking force is applied laterally to the joint ring. The amount of pulling force applied to the joint ring is less than that required to separate the joint ring from the concrete while the shocking force is applied in a direction transverse to the pulling force so that no harmful tensile shocking forces are transmitted to the concrete joint. The pulling force on the joint ring is variably applied and timed with the shocking force. The pulling force is applied at multiple locations to the joint ring, and the force at each location is monitored so that the pulling force is applied equally at all locations. 
     The advantages and features of the method and apparatus of the invention will become more evident from the detailed description of the preferred embodiment set forth hereinafter. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a section through the upper portion of a typical concrete product and showing the concrete joint; 
     FIG. 2 is a sectional view through a typical joint ring; 
     FIG. 3 is a side elevational view of the apparatus of the invention with some components removed and the concrete product and joint ring shown in section; 
     FIG. 4 is a perspective view of the apparatus of the invention; 
     FIG. 5 is an end elevational view viewing the apparatus from the direction indicated by the line A—A of FIG. 4; 
     FIG. 6 is a side elevational view of the clamping assembly with some components not shown for purposes of clarity; 
     FIG. 7 is a top or plan view of the clamping assembly of FIG. 6; 
     FIG. 8 is a top or plan view of the carriage for the clamping assembly; 
     FIG. 9 is a side elevational view of the carriage of FIG. 8; 
     FIG. 10 is a perspective view of the clamp trolley of the carriage of FIGS. 8 and 9; 
     FIG. 11 is a perspective view of an inner clamp pad; 
     FIG. 12 is a bottom plan view of the pull beam assembly and showing the carriage drive mechanism; 
     FIG. 13 is a side elevational view of the puller beam assembly of FIG. 12; 
     FIG. 14 is an end elevational view of the puller beam assembly; 
     FIG. 15 is a perspective view of a carriage that forms a part of the puller bit assembly; 
     FIG. 16 is a side elevational view of the carriage of FIG. 15; 
     FIG. 17 is a perspective view of a subassembly showing the puller bit; and 
     FIG. 18 is a simplified schematic diagram of that portion of the hydraulic system that controls the pull cylinders. 
    
    
     DETAILED DESCRIPTION 
     As will be understood by those skilled in the art, concrete pipe, manhole segments, and similar products are produced by well known methods in which concrete is poured into a form created by the use of a core and jacket to form a concrete product of the desired size and configuration. After the form is filled with concrete, a joint forming ring is pressed into the wet concrete at the top of the form, and the joint ring is left in place during the curing of the concrete. An example of concrete pipe making machines are illustrated in Schmidgall U.S. Pat. No. 4,708,621 and Schmidgall U.S. Pat. No. 5,234,331. After the concrete product has cured, the joint ring must be removed. The invention relates specifically to the apparatus described hereinafter for removing the joint forming rings from the cured concrete product. The joint rings must be removed from the concrete products without damaging the concrete joint formed as a part of the product. If the concrete joint is damaged, the damaged product will have to be discarded which is a monetary loss to the manufacturer. 
     Referring first to FIGS. 1,  2  and  3 , there is illustrated a concrete product such as a concrete segment  10  for a manhole. A section of the upper portion of the segment is shown in FIG.  1 . At the top of the segment  10  is formed a joint  12  of a standard configuration. As previously indicated, the joint  12  is formed by placement of a joint ring  14  in the top of the concrete after it is poured into the form to produce the concrete segment, with the joint ring  14  remaining in place until the concrete has cured. FIG. 2 is a sectional view of a typical joint ring  14  which has a groove  16  around its outer surface. The inner surface  18  of the joint ring  14  is shaped to produce the desired shape of the concrete joint  12 . FIG. 3 illustrates the joint ring  14  in place at the top of the concrete segment  10 . 
     Referring now to FIGS. 3,  4  and  5 , the main components of the apparatus are illustrated. The apparatus includes a vertically extending central beam  20  that provides for connection to suitable handling equipment capable of raising and lowering the joint ring puller apparatus and then moving the joint ring to a desired location for cleaning and storage. Such handling equipment is well known to those skilled in the art and does not form a part of the invention. The central beam  20  may form a part of the handling equipment, but in any event, the beam  20  is suitably connected by plates  22  to the clamping assembly  28  as best seen in FIG.  4 . 
     The apparatus of the invention includes two main assemblies, a puller beam assembly  26  and a clamping assembly  28 , the latter providing for holding the concrete segment  10  in position and resisting the pulling forces exerted by the puller beam assembly  26  during the joint ring pulling operation. FIGS. 5-11 illustrate the clamping components in which a clamp beam  30  supports at its lower end tracks  36  upon which ride clamp carriages  38 . The clamp beam  30  also supports at its lower end cylinders  39  which power the clamp carriages  38 . The clamp beam  30  at its lower end also supports tracks  36  upon which ride clamp trolley carriages  38 . As best seen in FIGS. 8-10, each clamp carriage  38  is comprised of an inner clamp  40  and a clamp trolley  42 . The inner clamp  40  includes an open housing  44  that provides tracks  46  inside of the housing upon which ride the wheels  41  of the clamp trolley  42 . The housing  44  also supports wheels  48  which ride on the tracks  36  of the clamp beam  30 . The clamp carriages  38  are each mounted at opposite ends of the clamp beam  30  with the wheels  48  engaging the tracks  36 . At each end of the clamp beam  30  are secured the sprockets  32  which synchronize and guide the endless chain  34 . Each of the clamp trolley carriages  38  is connected to the chain  34 , the carriages  38  being connected on opposite sides of the chain  34  so that when one carriage  38  moves outwardly the other carriage  38  will also move outwardly, and similarly, when one of the trolley carriages  38  moves inwardly, the other trolley assembly will also move inwardly. The chain  34  therefore synchronizes the movement of the trolley carriages  38 , being powered by cylinders  39 . 
     Each of the inner clamp assemblies  40  has an inner clamp pad  53  with a friction surface  52  affixed to a bracket  54  depending from the inner clamp assembly  40 . Each of the inner clamp pads  53  is mounted on the bracket  54  so as to pivot about a horizontal axis. Similarly, an outer clamp pad  57  having a friction surface  55  is mounted about a horizontal pivot on a bracket  58  depending from the clamp trolley  42 . As best seen in FIGS. 8 and 9, a hydraulic cylinder  60  has one end secured to the housing  44  of the inner clamp assembly  40  with the other end secured to the clamp trolley assembly  42 . The cylinder  60  operates to move the clamp trolley  42  relative to the inner clamp  40 . Thus, when the clamp beam  24  is lowered over a manhole or concrete segment  10  for removal of the joint ring  14 , the inner clamp assemblies  40 , carrying the clamp trolley assemblies  42 , will be moved to position the inner clamp pads  53  inside of the concrete segment  10  with the clamp trolley assemblies  42  being positioned by the hydraulic cylinder  60  so that the outer clamp pads  57  are outside of the walls of the concrete segment  10 . As illustrated by the dotted lines in FIG. 3, the inner clamp assemblies  40  are moved outwardly until the inner clamp pads  53  engage the interior wall of the concrete segment  10 . The hydraulic cylinders  60  will then move the clamp trolley assemblies  42  inwardly until the outer clamp pads  57  engage the outer surfaces of the wall of the concrete segment  10 . This will then hold the concrete segment  10  sufficiently firm to resist the forces of the joint pulling assembly which will now be described. 
     Referring now to FIGS. 3,  4 , and  12 - 17 , there are illustrated the basic assemblies and subassemblies for gripping and pulling the joint ring  14 . Referring first to FIGS. 3,  12 ,  13  and  14 , there is shown the puller beam assembly  26  with some components removed and not shown for purposes of clarity. The pull bar  24  supports a housing  61  that is movable relative to the pull bar  24  by hydraulic cylinders  63 . The housing  61  supports tracks  62  upon which ride pull trolleys, a drive pull trolley  64  and a slave pull trolley  66 . The trolleys  64  and  66  are shown in detail in FIGS. 15,  16  and  17 , and they are substantially identical in construction, and therefore, only the drive trolley  64  is shown. Each of the trolleys  64  and  66  have wheels  68  that engage the tracks  62 , the wheels  68  being mounted on a housing  70  that includes two spaced apart vertical walls  72 . The trolleys  64  and  66  are engaged and driven by drive screws  74  and  76  respectively. Drive screw  74  is driven by a hydraulic motor  78  mounted at the outer end of the housing  61 , and the drive screw  74  is connected through a drive coupling  80  which in turn causes the drive screw  76  to rotate with the drive screw  74 . The drive screw  74  is left-hand threaded while the drive screw  76  is right-hand threaded. This thus allows the drive pull trolley  64  and the slave pull trolley  66  to move in synchronization toward and away from each other under the control of the hydraulic motor  78 . 
     As previously indicated, the trolleys  64  and  66  include a housing  70  having vertical walls  72  upon which the wheels  68  are mounted. The drive screw  74  extends through a drive nut (not shown) mounted in a bearing  82 . Such drives are well known to those skilled in the art. Secured to the lower end of each of the pull trolleys  64  and  66  is a joint ring puller subassembly  86  (FIG.  17 ). The subassembly  86  includes two spaced apart parallel mounting plates  88  that extend substantially vertically when assembled to the pull trolley  64 . As best seen in FIG. 17, the mounting plates  88  have elongated vertically extending grooves  90  so that when the plates  88  are positioned inside of the vertical walls  72  of the pull trolley assembly  64 , cam followers (not shown) extending inside of the vertical walls  72  and secured to the walls  72  by fasteners  92  will be engaged in the grooves  90 . This allows the joint ring pull assembly  86  to move upwardly and downwardly relative to the pull trolley  64 . In order to control and power movement of the puller subassembly  86 , a hydraulic cylinder  94  is secured to a mounting plate  96  that forms a part of the housing  70 , and the operating rod (not shown) of the hydraulic cylinder will be secured to the cross members  98  (FIG. 17) that are secured to the mounting side plates  88 . 
     The puller subassembly  86  includes a pull bit mounting assembly  100  to which are attached the pull bits  102 . The pull bit mounting assembly  100  is mounted for swingable movement about a vertical axis by a pivot pin  104 . This permits the pull bits  102  to pivot and securely and properly engage in the groove  16  of the joint ring  14 . 
     As best seen in FIG. 17, the pull bits  102  are spaced apart, and extending between them is a pneumatic hammer  110  that drives a hammer butt  108 . The pneumatic hammer  110  drives the hammer butt  108  laterally against the joint ring  14  at the appropriate time as described hereinafter. 
     As illustrated in FIGS. 12 and 13, to assist in proper positioning of the apparatus of the invention relative to a cured concrete segment  10  containing a joint ring  14 , there are mounted at opposite ends of the pulling beam assembly  26 , transversely extending arms  112  at the outer edges of which are positioned photocells  114 . Photocells  114  are installed in pairs on opposite corners so that a transmitter  116  is positioned at the outer end of one arm and a receiver  118  at the other end of the same arm. Thus, both beams emitted from the photocells  114  travel across the center of the pull bar  24 . Thus, the beams from the photocells  114  can be used to vertically position the apparatus over the concrete segment  10  the joint ring  14  of which needs to be removed. 
     Once the apparatus is properly positioned over a concrete segment  10 , and using the hydraulic cylinder  63 , the puller beam assembly  26  is lowered to the correct elevation with the pull bits  102  opposite the groove  16  in the joint ring  14 . The hydraulic motor  78  is then actuated to drive the drive screws  74  and  76  and thereby move the drive pull trolley  64  and slave pull trolley  66  inwardly until the pull bits  102  are engaged in the groove  16  of the joint ring  14 . The clamping assembly  28  is then utilized to position the inner clamp pads  53  inside of the concrete segment  10  and the outer clamp pads  57  positioned outside the concrete segment  10 . The hydraulic cylinders  39  are then actuated to move the inner clamps  40  outwardly until the inner clamp pads  53  are engaged with the inside surface of the concrete segment  10 . Subsequently, the hydraulic cylinder  60  inside of the drive trolley  42  is actuated to move the drive trolleys  42  inwardly until they engage the outer surface of the concrete segment  10 . The inner clamp pads  53  and outer clamp pads  57  will then apply a clamping force to the concrete segment  10  sufficient to hold the segment  10  stationary during the joint ring pulling process. The hydraulic cylinders  94  are then actuated to apply an initial tensile force to the joint ring  14 . This initial tensile force is less than that required to separate the joint ring  14  from the concrete joint  12 . Each pull bit cylinder  94  is supplied with a predetermined pressure by pressure relief valve  119  for the particular concrete segment  10  being processed, and the pull bits  102  are moved upwardly and independently until the bits of each of the puller assemblies  86  firmly engage the joint ring groove  16 . As the pull bits  102  in each of the puller assemblies  86  are so engaged, the pressure in each cylinder  94  increases to a predetermined pulling pressure as monitored by means of a pressure transducer  120  (FIG.  18 ), after which a directional control valve  122  supplying the hydraulic fluid to each cylinder  94  is closed. When the valve  122  for each pull cylinder  94  is closed, pressure is trapped in the cylinder  94 . The hydraulic circuit is equipped with an accumulator  124  that will maintain the pressure in the pull cylinders  94  while limiting the distance that each pull cylinder  94  can travel. By thus limiting the travel of the pull cylinders  94 , the joint ring  14  can be slightly separated from the concrete joint  12  without traveling far enough to possibly bind the joint ring  14  on the concrete joint  12 , which binding is a major cause of breakage of the joint  12 . Thus, the independent control of each pull bit cylinder  94  ensures that the joint ring  14  is pulled evenly, and any misalignment between the two joint puller assemblies  86  and the joint ring  14  is compensated for in this manner. Without independent control of each of the pull cylinders  94 , there is a greater risk of the joint ring  14  binding and damaging the concrete joint  12 . 
     After the pull bit control valve for each cylinder  94  closes and the tensile force is thus maintained on the joint ring  14  by the pull bits  102 , the pneumatic hammers  110  are actuated to apply a lateral force through the hammer butts  108  against the joint ring  14  in order to break the bond between the joint ring  14  and the concrete joint  12 . By applying the shock force laterally, the concrete joint  14  is protected from breakage. The pressure transducers  120  are monitored for a pressure decrease which will indicate that the joint ring  14  has broken free from the concrete joint  12 . The volume of oil in the accumulator  124  of the hydraulic circuit thus allows only a small vertical separation of the joint ring  14  from the concrete joint  12 . When the drop in pressure is thus sensed by transducer  120 , the puller beam assembly  26  is then lifted vertically by cylinders  63  to completely separate the joint ring  14  from the concrete joint  12  thus completely the pulling process. When the pulling process is complete, the pressure on the hydraulic cylinders  60  holding the inner clamp pads  53  and outer clamp pads  57  is released, and the hydraulic cylinders  39  are actuated to withdraw the clamp carriages  38  and  40 . The entire apparatus is then lifted from the concrete segment  10 , carrying with it the joint ring  14  for movement to a cleaning and storage area. 
     Having thus described the invention in connection with the preferred embodiments thereof, it will be evident to those skilled in the art that various revisions can be made to the preferred embodiments described herein without departing from the spirit and scope of the invention. It is my intention, however, that all such revisions and modifications that are evident to those skilled in the art will be included within the scope of the following claims.