Abstract:
Methods for removing accretions of cured concrete from within a mixing drum are herein disclosed. One method includes an inserting impact tool mounted upon a boom into the interior of the mixing drum, addressing a bit of the impact tool to an accretion adhered to the inner surface of the mixing drum, and actuating the impact tool to apply a force to the accretions through the bit so as to remove the accretion from the interior surface of the mixing drum.

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/564,634, filed on Apr. 22, 2004, and is a continuation of U.S. application Ser. No. 11/110,003, filed Apr. 20, 2005, now abandoned, which are hereby incorporated herein in their entireties by reference. 
    
    
     FIELD 
     The present invention relates to an articulating impact mechanism used to remove concrete accretions from the interior of mixing drums. More particularly, the present invention relates to an impact hammer mounted upon an extendable boom, the impact hammer being mounted so as to be able to remove accretions from substantially the entire interior of the mixing drum. 
     BACKGROUND 
     At present the only cost-effective way of removing concrete accretions from within a mixing drum involves manually removing the accretions using sledgehammers and pneumatic hammers and chippers. This operation is not only expensive in terms of man-hours expended, but is also highly dangerous in that the noise generated in removing accretions from the interior of a mixing drum is horrendous, the fins mounted within a mixing drum can be sharp and therefore dangerous, the air-quality with in the mixing drum is bad due to the dust generated, and the likelihood of accident with the tools used to remove the accretions is relatively high. 
     Numerous methods have been suggested to remove accretions from within mixing drums. One such method involves rapidly striking the exterior of a mixing drum in order to loosen accretions within the drum. Not only does this method risk damaging the drum itself, but also many accretions may not be loosened by this method and manual removal of the remaining accretions will still be required. Another mechanism applies microwaves to the accretions within the mixing drum in hopes that heating the residual water within the accretions will cause the accretions to breakup. While the use of microwaves does remove at least some of the problematic accretions, the application of microwaves is of limited effectiveness and is also prohibitively expensive. 
     Other devices include mechanisms that mount an impact hammer thereon for the purpose of removing accretions from the interior of a silo, for removing the firebrick from the interior of a metal pouring crucible, and for chipping away at the surface of the rock in a mine. None of these devices have the necessary articulation that would allow them to reach all of the interior surfaces of a mixing drum having mixing fins mounted therein. While the crucibles used in steel making operations are roughly the same size and shape as a concrete mixing drum, concrete mixing drums include mixing fins on their interior, thereby creating a complex shape around which the tool must navigate. Concrete mixing fins are generally helical in shape and extend inwardly away from the inner surface of the mixing drums. Concrete accretions that form on or around these fins are difficult to access for the types of prior art devices described hereinabove, which are designed to access relatively uncluttered surfaces. 
     Accordingly, it is an object of the present invention to provide a device for removing accretions from within a mixing drum that has an impact tool that can be arranged to access substantially the entire interior of the drum having mixing fins mounted therein. Furthermore, it is an object of the present invention to provide a device that may readily be used with mixing drums of various designs without modification. Another object of the present invention is to provide a device that can readily be brought to a remote location to remove accretions from a mixing drum or which may be mounted permanently in a single location for the purpose of removing accretions from a mixing drum. 
     These and other objects, aspects, features and advantages of the present invention will become more fully apparent upon careful consideration of the following Detailed Description of the Invention and the accompanying Drawings, which may be disproportionate for ease of understanding, wherein like structure and steps are referenced generally by corresponding numerals and indicators. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partially cutaway side view of a prior art concrete mixing truck having a mixing drum mounted thereon; 
         FIG. 2  is a cross-section of a mixing drum showing one embodiment of an accretion removing device in relation thereto; 
         FIG. 3  is a schematic view of one embodiment of an impact tool of the accretion removing device of the present invention; 
         FIG. 4  is another embodiment of the device as shown in  FIG. 3  that includes a rotating wrist joint; 
         FIG. 5  is another embodiment of the device as shown in  FIG. 3  that includes a rotating arm coupled between a boom and an impact tool of the device; 
         FIG. 6  is a schematic side view of an embodiment of the accretion removing device showing the impact tool coupled to an elongate boom; 
         FIG. 7  is a schematic representation of one embodiment of the device mounted upon a vehicle, the device being addressed to a mixing drum mounted upon a concrete mixing truck; 
         FIG. 8  is a schematic representation of one embodiment of the device mounted upon a fixed stand, the impact tool of the device being addressed to the interior of a mixing drum mounted upon a concrete mixing truck that is positioned upon inclined surface; 
         FIG. 9  is a schematic, side view of another embodiment of the accretion removing device having an elongate, rotating boom; and, 
         FIG. 10  is a schematic side view of the embodiment of  FIG. 9  showing the opposing side of the accretion-removing device of the present invention. 
         FIG. 11  is a side elevation of another embodiment of the device wherein the boom is mounted to an extendable arm. 
         FIG. 12  is a close-up, perspective view of the tool of the accretion removing device. 
     
    
    
     All figures are drawn for ease of explanation of the basic teachings of the present invention only; the extensions of the figures with respect to number, position, relationship, and dimensions of the parts to form the preferred embodiment will be explained or will be within the skill of the art after the following teachings of the present invention have been read and understood. Further, the exact dimensions and dimensional proportions to conform to specific force, weight, strength, and similar requirements will likewise be within the skill of the art after the following teachings of the present invention have been read and understood. 
     Where used in the various figures of the drawings, the same numerals designate the same or similar parts. Furthermore, when the terms “top,” “bottom,” “upper,” “lower,” “first,” “second,” “inside,” “outside,” and similar terms are used herein, it should be understood that these terms have reference only to the structure shown in the drawings as it would appear to a person viewing the drawings and are utilized only to facilitate describing the invention. 
     DETAILED DESCRIPTION 
     Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention, which may be embodied in other specific structure. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims. 
     Turning first to  FIG. 1 , there is illustrated a typical prior art concrete mixing truck  10  having a mixing drum  12  mounted thereon. Note that the mixing drum  12  is mounted upon the truck  10  at an angle such that its closed end  14  is lower than its open end  16 . Ingredients for concrete are deposited in the drum  12 , and mixed concrete is removed therefrom, through the open end  16  by means of a series of funnels and troughs  18 . Note also that the truck  10  illustrated in  FIG. 1  is of a variety in which the mixing drum is  12  is arranged such that the open end  16  thereof is located at the rear of the truck  10 . The present invention may be used with this type of truck  10  or with another variety of truck (not shown) in which the mixing drum  12  is reversed such that the open end  16  of the drum  12  faces forward upon the truck  10 . The present invention may also be used to remove accretions from mixing drums  12  that are mounted in a fixed location, such as the batch drums (not shown) commonly used in a concrete plant. 
       FIG. 2  illustrates a typical mixing drum  12  and how the accretion-removing device  20  of the present invention is addressed thereto. As can be seen, the drum  12  has a closed end  14  and open end  16 . The drum  12  is angled such that ingredients to be mixed within the drum  12  will congregate closer to the central bulge  15  of the drum  12  nearer the closed end  14  thereof. The drum  12  is also provided with a hatch or manway  17  that allows access to the interior of the drum without having to enter through the open end  16  of the drum  12 . The drum  12  is also provided with a number of fins  19  that are generally helical in arrangement. The fins  19  are further arranged so as to create a shear forces within the admixture deposited within the mixing drum  12 . These shear forces aid in mixing the concrete and act to selectively retain and remove the mixed concrete in and from the drum  12 , depending on the direction in which the drum  12  is rotated. 
     Over time, small quantities of concrete cure within the drum  12  and adhere to the inner walls and fins  19  thereof. Eventually, these accretions will begin to severely limit the performance of the mixing drum  12  as the drum  12  will become much heavier and the effectiveness of the fins in mixing the concrete within the drum  12  will be reduced. The greater weight of the drum  12  will increase the wear and tear on the drum  12  and truck  10  and the increased friction present within the drum  12  due to the accretions will negatively affect the mixing action of the drum  12  as well. Where a concrete mixing truck  10  is involved in an accident or the mechanism whereby the mixing drum  12  is rotated otherwise becomes inoperable, all or a significant portion of the cement within the mixing drum  12  may harden, thereby rendering the drum  12  entirely unusable. The abrasive nature of concrete being what it is, mixing drums  12  do have a limited life. However, the useful life of a mixing drum is long enough that accretions of concrete will build up to unacceptable levels long before the drum  12  must be replaced. Accordingly, it will be necessary to remove these accretions multiple times over the life of a particular mixing drum  12 . 
     As can be seen in  FIG. 2 , the accretion removing device  20  of the present invention may be inserted into the interior of the mixing drum  12  such that the striking tool  30  of the device  20  may be addressed to the accretions of concrete that are adhered to the inner surface of the drum  12  and to the fins  19 . In order to insert the device  20  into the drum  12 , there must be relative motion between the drum  12  and the device  20 . In one embodiment of the present invention, the device  20  is mounted upon a mobile platform such as a truck  24 . In this embodiment, the device  20  will be inserted into the drum  12  by backing the truck  24  up to the drum  12 . The device  20  will be mounted or positioned at a sufficient height with respect to the open end  16  of the drum  12  so as to allow the device  20  to be inserted through the open and  16  of the drum  12 . Note also that the device  20  must be rotatable about axis  26  as shown by arrows  28  so as to match the angle of the drum  12 . It is likely that the device  20  will be rotated about the axis  26  as the truck  24  backs up to the drum  12  so that the angle of the device  20  with respect to the drum  12  may be continuously corrected so as to avoid striking the interior drum  12  or fins  19  with the device  20 . 
     Another embodiment of the device  20  may be mounted upon a fixed platform (see  FIG. 8 ) so that a concrete mixing truck  10  may be addressed to the stationary device  20 . Again, the device  20  will be rotated as the concrete mixing truck  10  is moved towards the device  20  so as to match the angle of the device  20  with the angle of the drum  12 . In this embodiment of the device  20 , the device  20  may be mounted upon a fixed platform that is mounted upon the floor or upon a support that is mounted on an overhead structure suspended above the drum  12  (not shown). 
       FIG. 3  is a close-up schematic view of the impact tool  30  of the device  20 . The chassis  32  of the impact tool  30  is mounted upon a boom  34  of the device  20 . In one embodiment, the boom  34  will be arranged so as to allow the chassis  32  of the impact tool  30  to rotate approximately 270° about axle  39 . In one embodiment, this rotation is generally symmetric with respect the axis  40  (shown in  FIG. 5 ) of the boom  34 . This range of motion can easily be accomplished by constructing at least the end of the boom  34  of two parallel plates that allow the chassis  32  to rotate therebetween. In another embodiment of the present invention, the impact tool  30  will rotate through approximately 180° on axle  39 , the rotation being generally symmetric about axis  33 . 
       FIG. 4  illustrates another embodiment of the device  20  that further includes a “wrist” joint  36 . The a wrist joint  36  allows for rotation of the tool  30  about an axis defined by the length of the boom  34 ′. In one embodiment, the wrist joint  36  will enable the tool  30  to rotate at least 360° about the axis defined by the boom  34 ′. In yet another embodiment, the wrist joint  36  will enable the tool  30  to rotate up to 380° about the boom  34 ′. 
       FIG. 5  illustrates yet another embodiment of the device  20  in which a rotatable arm  38  is interposed between the boom  34  and a tool  30 . The arm  38  allows for more flexible positioning of the bit  35  of the tool  30 , thereby increasing the effectiveness of the device  20 . In some applications, it may be necessary to be able to position the bit  30  such that it may attack accretions that are located at or near an axis  40  of the boom  34 . Note that the arm  38  is pinned to the boom  34  by an axle  42  or equivalent structure. Arm  38  may rotate with respect to boom  34  about the axle  42  and is actuated by a typical hydraulic or pneumatic actuator (not shown). Similarly, the tool  30  is joined to the arm  38  by axle  44  or equivalent structure. Tool  30  is free to rotate about axle  44  as described hereinabove. Note that the arm  38  may also be employed in conjunction with a wrist joint  36  such as the illustrated in  FIG. 4 . 
       FIG. 6  illustrates one embodiment of the present invention in which the tool  30  is mounted upon an elongate boom  34 . The elongate boom  34  is in turn coupled to an extendable arm  46  that is itself received within a tube  48 . Note that tube  48  and extendable arm  46  are adapted to support and manipulate the boom  34 . In one such embodiment, the extendable arm  46  and the tube  48  are part of a specially adapted hydraulic excavator of a type marketed by the Badger Equipment Co. of Winona, Minn. as a Series 460 HYDRO-SCOPIC™ hydraulic excavator. Note that a wrist joint  36  may be incorporated into the boom  34 , or into the extendable arm  46 . The embodiment illustrated in  FIG. 6  may be mounted upon a truck or other mobile platform such as a gantry crane or a wheel or tracked carriage; this embodiment may also be fixed in its location, being mounted upon a turntable that is itself secured to a concrete support or the like. 
     Where the device  20  is adapted to be brought to a mixing drum  12  for operation, the boom  34  may be too long for easy transport upon the roads. Accordingly, dismounting the boom  34  entirely from the device  20  may facilitate transport of the device  20 . Alternatively, the boom  34  may be provided with a hinge  37 . In this embodiment, the boom  34  may be folded upon itself so that the device  20  may be transported in compliance with state Department of Transportation rules. 
     In yet another embodiment, the boom  34  may be omitted in favor of an elongate extendable arm  46 .  FIGS. 9 and 10  illustrate another embodiment of the present invention in which the boom  34 ″ has a wrist joint  36  at its base end. 
       FIGS. 10 and 12  illustrate one embodiment for rotating the tool  30  about axis  39 . A rotary actuator  60  mounted on boom  34 ″ has a sprocket or sheave  62  mounted thereon. A chain or belt  64 , as the case may be, is passed around sprocket  62  and through an opening in the tubular boom  34 ″. The chain  62  is then passed around a second sprocket  66  that is located within the boom  34 ″. In one embodiment, sprocket  66  is a double sprocket, i.e. has two sprockets mounted side by side on the same axle and constrained to rotate with one another. A second chain  68  is passed around sprocket  66  and extends through boom  34 ″ to a third sprocket  70  mounted on axle  39  of tool  30  as can best be seen in  FIG. 12 . Rotation of the rotary actuator  60  is accordingly transferred by chains  64  and  68  to tool  30 . 
     Referring next to  FIGS. 7 and 8 , in operation, a preferred embodiment of the device  20  mounted upon a vehicle  50  may be addressed to the interior of a mixing drum  12  mounted upon a concrete mixing truck  10  by moving the vehicle  50  adjacent to the drum  12 . The device  20  is manipulated so that the tool  30  passes into the open end  16  of the drum  12 . Note that as the vehicle  50  is moved closer to the drum  12 , the boom  34  will likely need to be manipulated to prevent the tool  30  from striking the interior of the drum  12 . 
     Where the boom  34  has been omitted in favor of an extendable arm  46  having a travel length sufficient to address the tool  30  to the entire length of the interior of the drum  12 , the vehicle  50  will be positioned securely before the tool  30  is inserted into the mixing drum  12 . Note that in some circumstances it may be preferable to move the vehicle  50  with respect to the concrete mixing truck and that in other circumstances it may be preferable to move the concrete mixing truck  12  with respect to the vehicle  50 . However, where the length of travel of the extendable arm  46  or a similar structure upon which the tool  30  is mounted is not such that the tool  30  may be addressed to the entire length of the drum  12 , it will likely be necessary for the entire device  20  and drum  12  to move with respect to one another whether by moving the truck  10 , vehicle  50 , or, as indicated above, moving the device  20  itself with respect to the drum  12 . 
     In some embodiments, the device  20  is mounted at a height that is sufficient to allow the boom  34  and hence the tool  30  to be inserted into the interior of the drum  12  as described in conjunction with  FIG. 7 . However, where it is more economical to mount the device  20  lower to the ground, or where the vehicle  50  upon which the device  20  is mounted is significantly lower than the open end  16  of the drum  12 , it may be necessary to position the concrete mixing truck  10  at an angle with respect to the device  20 . In one embodiment, the device  20  may be installed in a fixed position adjacent to a sunken ramp  52 . The concrete mixing truck  10  is then positioned on the ramp  52  such that the boom  34  may be inserted into the interior of the drum  12  through open end  16 . Preferably, all embodiments of the device  20  will be mounted in such a way that the boom  34  upon which is mounted the tool  30  has at least three degrees of freedom; specifically, the booms  34 ,  34 ′, and  34 ″ may be rotated about a vertical axis such as that described by axis  54 , it may be raised and lowered as by rotation about pivot point  56 , and it may be extended and retracted along an axis defined by the extendable arm  46 . Depending on how the device  20  is mounted, and upon whether it includes a rotatable arm  38  and/or a wrist joint  36 , it is possible that the boom  34  may be mounted in a fixed position such that the boom  34  does not move at all. Alternatively, the boom  34  may be extended, retracted, and rotated about a vertical axis, or may be moved up and down by rotation or any combination of these three modes of travel. 
     In another embodiment of the device  20 , the boom  34 ″ is coupled to arm  46  by a coupling  100 . Coupling  100  includes a mounting post  102  that is secured by means of bolts  104  to the arm  46 . Bearing blocks  106  are mounted in an upper surface of the mounting post  104  and receive therein a shaft  108  of an upright  110 . Upright  110 , being coupled to mounting post  104  by bearings  106 , will rotate around an axis defined by shaft  108  and bearings  106 . 
     Arm  112  is coupled to and extends from mounting post  102 . Arm  112  is constructed such that a linear hydraulic or pneumatic cylinder  114  coupled between a distal end of the arm  112  and a tangential surface of the upright  110 , will rotate the upright  110  within bearings  106  to provide lateral adjustment of the boom  34 ″. What is more, the arm  112  and cylinder  114  may be adapted to rotate the boom  34 ″ into a stowed position in which the boom  34 ″ is essentially rotated into a position that is more or less a mirror image of the position of the boom  34 ″ as seen in  FIG. 11 . Boom  34 ″ is held in a cradle  118  that is rotatively coupled by pin joint  116  to upright  110 . Hydraulic or pneumatic cylinder  117  is coupled between the upright  110  and the cradle  118  to rotate the cradle  118  with respect to the upright  110  about pin joint  116 . 
     The boom  34 ″ is coupled to the cradle  118  by rotary bearings  120  such that boom  34 ″ may be rotated about its longitudinal axis. A rotary actuator  122  coupled between the cradle  118  and the boom  34 ″ rotates the boom  34 ″ with respect to the cradle  118 . 
     In some embodiments, the mounting post  102 , arm  112 , and cylinder  112  are omitted in favor of rotatively pinning the bottom end of the upright  110  directly to the arm  46 . In these embodiments, the lateral adjustment of the boom  34 ″ is accomplished by adjusting the lateral position of the arm  46 . 
     Where the device  20  is mounted upon a vehicle  50  having a low height, and where no ramp  52  is available, it may be possible to position the front or rear wheels of the concrete mixing truck  10 , depending upon the orientation of the drum  12 , upon a portable ramp (not shown) such that the angle of the drum  12  in the position of the open end  16  thereof may allow the entry of the device  20  into the interior of the drum  12 . 
     The tool  30  is preferably an impact tool operated by means of hydraulic or pneumatic pressure. Such tools are well known in the art and are commonly used in the construction and mining fields. The tool  30  includes a bit  33  the may be addressed to accretions of concrete deposit on the interior of the drum  12 . It is preferable to utilize a bit  33  that is somewhat blunt as a sharp bit  33  may accidentally puncture the walls of the drum  12 . This is particularly problematic in older drums  12  in which the abrasive nature of the concrete mixed therein has significantly eroded the metal walls of the drum  12 . 
     The mechanism whereby the boom  34  may be extended, rotated laterally, and rotated vertically, is preferably a hydraulic mechanism, though it is to be understood that pneumatic, electrically actuated, or manually operated mechanisms may be used as well. Such mechanisms are well known in the art and are commonly in use in construction and mining fields. 
     In operation, it is desirable for an operator of the device  20  to visually inspect the removal of the accretions as work proceeds. In one embodiment of the device  20 , the operator of the device  20  is located remotely with respect to the vehicle  50  upon which the device  20  is mounted. The operator manually manipulates the controls that actuate the device  20 . The operator views the work as it progresses using a closed circuit television camera  80  and monitor (not shown). Alternatively, the operator may be provided with remote controls and may view the progress of the device  20  through the manway  17  or through the open end  16  of the drum  12 . It is also envisioned that an electronic controller (not shown) may be programmed with the geometry of a given mixing drum  12 . The electronic controller, using the programmed geometry information, is able to automatically remove the accretions from the drum  12  on the basis of a predetermined set of instructions. 
     In addition to video monitoring, other sensors may be utilized to accurately determine the position of the tool  30  and bit  33 . These may include, but are not limited to laser range finders, optical sensors, gyroscopes, linear and rotary encoders, and the like. 
     In addition to removing accretions that accumulate on the interior surfaces of the mixing drum  12 , the device  20  may be utilized to remove large, solid masses of cured concrete from a mixing drum  12  where an accident or malfunction has allowed the concrete within the mixing drum  12  to cure. 
     It is envisioned that a single vehicle  50  having a device  20  mounted thereon may be used to service the large number of concrete mixing trucks  10  over a large area. In this way, no single cement company or contractor will be required to purchase, operate, and maintain the device  20 . Alternatively, where it is economically feasible, the operator of one or more concrete mixing trucks  10  or the operator of a cement mixing plant, may install a device  20  in a particular fixed location to which the concrete mixing trucks  10  are brought to have accretions removed from their mixing drums  12 . 
     In operation, the device  20  and the mixing drum  12  are first positioned with respect to one another such that the tool  30  may be inserted into the interior of the drum  12 . As indicated above, this may involve moving the vehicle  50  upon which the device  20  is mounted toward the concrete mixing truck  10 , moving the concrete mixing truck  10  toward the device  20  (regardless of whether the device  20  is mounted upon a vehicle  50  or upon a fixed or semi-fixed platform), or extending an arm  46  so as to inserted the tool  30  into the mixing drum  12 . 
     Once the tool  30  has been inserted into the interior of the mixing drum  12 , the tool  30  is manipulated to bring the bit of the tool  30  into contact with the accretions of concrete within the drum  12 . The tool  30  is then actuated so that the bit  33  will break up the accretions. Once all of the accretions have been removed from the interior surfaces of the drum  12 , or where the loose accretions broken off from the interior of the drum  12  interfere with the ability of the bit  30  to remove more accretions, the device  20  will be removed from the interior of the drum  12  and the loose concrete will be removed therefrom. Loose concrete in the drum  12  may be removed manually or the drum  12  may be rotated to remove them in the same way that uncured, plastic concrete is removed from the drum  12 . Alternatively, a vacuum type mechanism (not shown) may be used to remove loose accretions from the drum  12 . Where accretions remain adhered to the drum  12 , the device  20  may be reinserted into the drum  12  to loosen the remaining accretions. 
     It is desired to adapt the device  20  so that it may access the entire interior surface of the mixing drum  12  including its fins  19  without requiring the drum  12  to be moved or rotated. However, in some embodiments, the range of motion of the device  20  may be limited such that the device  20  may address only a portion of the drum  12  at any given point in time. For example, the tool  30  may be addressed to a portion of the interior of the drum whereafter the drum  12  is rotated to allowed the tool  30  to address another portion of the drum  12 . Similarly, the tool  30  may be positioned longitudinally with in the drum  12  by moving the drum  12  and/or the device  20  with respect to one another. 
     The bit  33  is preferably fashioned of steel, but may also be fashioned of a relatively hard, resilient material that is sufficiently rigid to break up concrete accretions, but which is resilient enough to somewhat reduce the noise engendered by the bit  33  striking the steel walls of the mixing drum  12  and which will be less likely to pierce the sides of drum  12 . Noise created by the activity of removing accretions and interior of a mixing drum  12  may further be damped by carrying out the procedure entirely inside an insulated building or tent, or by placing a material over the exterior of the mixing drum  12  to damp out vibrations. 
     Since the invention disclosed herein may be embodied in other specific forms without departing from the spirit or general characteristics thereof, some of which forms have been indicated, the embodiments described herein are to be considered in all respects illustrative and not restrictive. The scope of the invention is to be indicated by the appended claims, rather than by the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are intended to be embraced therein.