Abstract:
Apparatus and process for marking a surface with a highly visible and substantive mark comprising mixing a dry granular, free-flowing superabsorbent polymer powder with liquid, preferably water, and dye to form a semi-solid gel and depositing the gel onto the surface to be marked. The marking apparatus comprises a chamber for mixing the gel and a ram used to eject the gel from the chamber without excess mechanical agitation and without causing significant breakdown of the gel. The dye makes the gel very visible, the bulk of the gel makes it more easily visible, the nature of the gel makes it temporary; easily dispersed with time, sunlight or water.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This is a division of application Ser. No. 09/054,397, filed Apr. 3, 1998 now U.S. Pat. No. 6,026,135. Reference numerals used in the parent application have been retained herein for cross-reference consistency. 
     This application claim benefit to provisional application Ser. No. 60/041,929 Apr. 4, 1997. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to apparatus and method for depositing a substantive, highly visible, yet temporary mark on a surface, the mark being formed of a superabsorbant polymer, water and dye mixture. 
     BACKGROUND OF THE INVENTION 
     While the invention is described in the context of marking the location of mines, it is anticipated that the novel mark can be applied wherever a location needs to be identified. 
     In the process of identifying mines, it needs to be marked for subsequent neutralization, usually by digging it out of the ground. The existing line marking and other spray paint means are substantially without mass, are difficult to place on ground and are only visible if viewed substantially straight on. Further, paints and the like are usually associated with toxicity and are semi-permanent. There is opportunity and a need for a temporary, environmentally friendly and highly visible marking scheme. 
     SUMMARY OF THE INVENTION 
     It is critical that the location of a possible mine be reliably marked for subsequent neutralization. Once an object has been confirmed as a mine, the object or the ground in which it lies is marked by placing a substantive, visible and temporary mark on the ground. 
     In a broad aspect, a process is provided comprising mixing a dry granular, free-flowing superabsorbent polymer powder with liquid, preferably water, and dye to form a semi-solid gel and depositing the gel onto the surface to be marked. The dye makes the gel very visible, the bulk of the gel makes it more easily visible, the nature of the gel makes it temporary; easily dispersed with time, sunlight or water. 
     The above process is effected using apparatus comprising a ram used to eject the gel from a mixing chamber without introducing excess mechanical agitation and thus without causing significant breakdown. Preferably the apparatus comprises a first cylinder with a ram moveably therein to alternately open to form a gel mixing chamber and then close to eject the gel contents. Further, a second cylinder and ram is provided, preferably directed through a manifold to supply the liquid. The manifold can also co-ordinate the introduction of liquid and dry polymer powder into the first cylinder. 
     The resultant mark is bulky and thus highly visible from the side. The mark&#39;s visibility continues for several hours and after its useful life, the mark degrades in an environmentally friendly manner, substantially disappearing completely in 48 hours under drying, sunlight or rain conditions. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic side view of a mine detecting vehicle; 
     FIG. 2 is a flow chart of the novel marking system; 
     FIG. 3 is a perspective view of the marking apparatus according to one embodiment of the marking system; 
     FIG. 4 is a perspective exploded view of the marking apparatus according to FIG. 3; 
     FIG. 5 a  is a cross-sectional view through the center of the mixing and discharge manifold according to FIG. 3; 
     FIG. 5 b  is a cross-sectional side view of the mixing and discharge manifold as sectioned through the center of the ram chambers according to FIG. 3; 
     FIG. 6 a  is a schematic cross-sectional view of the apparatus in the powder charging position; 
     FIG. 6 b  is a schematic cross-sectional view of the apparatus in the powder discharging position; 
     FIG. 7 is a cross-sectional view of a hydraulic actuator and ram used for both the water ram and the product ram; and 
     FIG. 8 is flow chart of the water and product ram cycles for taking on water and powder respectively, mixing and making the gel product and discharging the gel product. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Having reference to FIG. 1, a mine detector vehicle comprises leading sensors  2 ,  3 ,  4 , a remote-controlled detection vehicle  5 , a trailing sensor  6  and a following command vehicle  7 . The illustrated vehicle is described in great detail in the co-pending parent application. 
     The leading sensors identify targets of interest (“TOI”). The trailing sensor  6  is a device, mounted in a maneuverable trailer  20 , which is capable of confirming whether a TOI is a mine. 
     A marking system is located on trailer  20  and comprises a marking assembly  201  for placing a physical mark on the ground at the confirmed location of a mine. Subsequently, the mark is referenced for safely re-locating the mine for neutralization. 
     Having reference to FIGS. 2,  3 , a marking assembly  201  is provided comprising novel apparatus and method. Generally, as described below, a dry granular longchain polymer powder is mixed with a highly visible dye and water. The polymer swells to form a gel product having a wet volume about 20 times the dry powder volume. This highly visible gel product is deposited on the ground at the position which is to be marked. The gel product has a physical bulk which is more easily visible than is a substantially mass-less mark. Combined with a highly visible dye, the mark very effective. When placed on the ground to mark the presence of a mine, the location is safely and clearly marked for several or more hours before planned degradation lessens its effectiveness. 
     More specifically, and having reference to FIG. 2, the marking system comprises a gel production and marking assembly  201 , water supply tank  202  and pump  203 , a hydraulic power circuit  204  and a 24VDC controller  205 . 
     Turning to FIG. 3, the assembly  201  for making and depositing the gel product comprises a dry powder hopper  206 , a metering head  207 , a mixing and injecting manifold  208 , a water ram  209 , a gel product ram  210  and a gel product discharge tube  211 . The gel product or mark  212  is discharged onto the ground  213  from the discharge tube  211 . 
     In more detail and referring to FIGS. 3-6 b,  the hopper  206  is mounted atop a base plate  214 . The hopper  206  is located above the metering head  207  for permitting gravity discharge of its dry powder through a hopper discharge port  215  (seen in FIG. 6 a,    6   b ). The metering head  207  comprises: a guide block  217  sandwiched between a top metering plate  216  and a bottom isolating plate  218 . The metering head  207  itself is sandwiched between the hoppers base plate  214  and the manifold  208 . 
     The hopper&#39;s base plate  214 , metering plate  216 , guide block  217 , isolating plate  218  and manifold  208  are stacked and incorporate seals between each component. The hopper base plate  214 , guide block  217  and manifold  208  are in fixed space relation to each other using two opposing sets of four bolts  219  each, and are spaced from each other by the metering and isolating plates  216 ,  218 . The metering and isolating plates  216 ,  218  are laterally movable using a double acting hydraulic actuator  220 . The actuator  220  is connected to a slider bracket  221  which links the metering and isolating plates  216 ,  218  together for synchronous, sliding movement. 
     The guide block  217  has a “H”-shaped cross section for forming a pair of upper side walls  222  and a pair of lower side walls  223  for containing the metering and isolating plates  216 ,  218  during sliding movement. 
     Each of the hopper base plate, metering plate, guide block, isolating plate and manifold have complementary ports formed therethrough for gravity passage of the dry powder. Dry powder discharges through the hopper port  215 . A metering port  224  is formed in the metering plate  216 . Port  225  is formed through the guide block  217 . Port  226  is formed through isolating plate  218 . Finally, a port  227  is formed through the manifold  208 . 
     The hopper base plate port  215  is laterally shifted from the guide block and manifold ports  225 ,  227  so that at no time is there a continuous path from the hopper  206  through to the manifold  208 . The guide block port  217  is always aligned with the manifold port  227 . 
     The metering and isolating plates  216 ,  218  are movable between a powder charging position (FIG. 6 a ) and a powder discharging position (FIG. 6 b ). 
     In the powder charging position, the metering port  224  (and isolating port  226 ) are actuated with actuator  220  so as to align with the hopper base plate port  215 . This action takes the metering and isolating ports  224 ,  226  out of alignment with the guide block port  225 . 
     In the discharging position, the metering port  224  (and isolating port  226 ) are actuated to align with the guide block port  225  for discharging metered powder through the manifold port  227 . 
     Best seen in FIG. 4, oblong seals  228 ,  229  are situated in the two interfaces between the hopper base plate  214 , metering plate  216 , and guide block  217 . The oblong shape of the two seals  228 ,  229  maintains a continuous seal between the hopper base plate port  215  and metering plate port  224 , and between the metering plate port  224  and guide plate port  225  throughout the powder charging and discharging positions. 
     Circular seals  230 ,  231  are situated in the two interfaces formed between the guide block  217 , the isolating plate  218  and the manifold  208 . The isolating plate port  226  moves into the circular sealed area in the discharge position. In the powder charging position, the isolating plate port  226  moves out of the sealed area for isolating the manifold  208  from the metering head  217 . 
     Beneath the manifold  208  is mounted a pair of hydraulically operated rams; the water ram  209  and the gel product ram  210 . Best seen in FIG. 7, rams  209 ,  210  have pistons  232  movable within cylinders  233 . The pistons  232  have annular seals  234  for forming a water chamber  235   a  and product chamber  235   b  within their respective cylinders  233 . The pistons  232  are independently operated with double acting hydraulic actuators  236 . The cylinders  233  seal to the underside of the manifold  208 , secured with long studs  245 . Each hydraulic actuator  236  has a piston rod  237  having a first end  238  and a second end  239 . A hydraulic piston  240  and annular piston seals  241  are mounted at the piston rod&#39;s first end  238 . The hydraulic piston  240  is operable within a hydraulic cylinder  242  separated from the water and product chambers  235   a,    235   b  by bulkhead  243  and annular seal  244 . The water and product pistons  232  are mounted at the second ends  239  of the piston rods  237 . A first hydraulic port  246  (FIG.  3  and fancifully depicted in dotted lines in FIG. 7) in the bulkhead  243  introduces hydraulic fluid to the hydraulic actuator  236  to drive the piston rod  237  and its respective water and product piston  232  away from the manifold  208 , forming their respective water and product chambers  235   a,    235   b.  A second hydraulic port  247  introduces hydraulic fluid to the hydraulic actuator to drive its respective water and product piston  232  towards the manifold  208  for ejecting the contents of their respective chambers  235   a,    235   b.    
     The manifold port  227  extends completely through the manifold  208  from the metering head  207  to the product chamber  235   b  of the product ram  210  located directly below the port  227  (FIGS. 4,  6   a,    6   b ). 
     Having reference to FIGS. 5 a,    5   b,  the manifold  208  routes powder, water and product gel to and from the water and product rams  209 ,  210 . A first passage  250  extends from the water ram  209  and chamber  235   a,  through the manifold  208  and into the product ram  210  and chamber  235   b.  The water passage  250  is interrupted with a valve, such as a check valve  251  for permitting water flow from the water chamber  235   a  to the product chamber  235   b  but not in the reverse direction. The first passage  250  exits into the product chamber  235   b  through discharge  252 , angled downwardly towards the product ram&#39;s piston  232 . A second passage  253  extends from the product chamber  253   b,  through the manifold  208  and to a gel product outlet port  254 . A product discharge tube (FIG. 3) conducts gel product from the outlet port  254  to the marking site. Port  255  is provided for routing water supply through a third passage  256  to the water chamber  253   a.  The third passage  256  is fitted with a check valve  257  to permit water to enter the water chamber  253   a  but not exit that way. 
     A superabsorbant powdered long chain polymer is used such as Potassium Polyacrylate, polycarbonate or polymer available under the tradename “DriMop” or SaniSorb” from Multisorb Technologies, Inc., Buffalo, N.Y. These and other similar polymers are often used in liquid spill control and activate when mixed with water to form a gel product. When mixed at ratio of about 95:5 water:powder by volume the polymer powder absorbs nearly 20 times its volume in water and forms a semi-solid gel. The gel is not robust and breaks down under mechanical agitation and UV exposure. About 97% of the polymer is biodegradable. 
     Environmentally friendly, forestry-marking dyes are available in liquid form as “Fluorescent Dye” from Forestry Suppliers, Inc., Jackson, Miss. Some dyes are suitable for use with potable water such as “Rhodamine WT”. 
     In operation, dye is premixed with water (for Fluorescent Dye, concentrations of about 0.1% are sufficient). The hopper is filled with powdered polymer. 
     Having reference to FIGS. 6 a,    6   b,  the metering and isolation plates  216 ,  218  are cycled between the charging and discharging positions in the respective figures. The position of the metering and isolating plates  216 ,  218  dictates the timing of product ram  209  charging with powder and the ejection of gel product. 
     The charging/discharging cycle is illustrated in FIG.  8 . 
     When actuated to the charging position (FIG. 6 a ), the following occurs. The ⅞″ diameter by ½″ deep metering port  224  is moved to the charging position under the hopper discharge port  215  for accepting a metered volume of the polymer powder. The isolation plate  218  seals the manifold  208  from the metering head  207  and hopper  206 . 
     While the metering and isolation plates  216 ,  218  are still at the charging position, the following steps can occur. The water ram  209  is actuated to move water from the water chamber  235   a,  through the first passage  250  and into the product chamber  235   b  for mixing with polymer powder present from the previous cycle. Air is bled from the product chamber  235   b  while water is transferred. The water and powder mix to form the gel product. The product ram  210  is then actuated for pressurizing and ejecting the gel product out through the manifold&#39;s second passage  253  and the discharge tube  211  without subjecting the gel product to excessive mechanical agitation or flow-back into the metering head  207  or hopper  206 . 
     When actuated to the discharging position (FIG. 6 b ), the following occurs. The metering plate port  224  is positioned to discharge the metered polymer through the aligned guide block  217 , isolation plate  218  and manifold ports  227  so that it enters the product chamber  235   b  of the product ram  210 . The metering plate  216  seals the hopper discharge port  215 . As it is disadvantageous to contaminate the guide block isolation plate ports  217 ,  218  of the metering head  207 , it is necessary to return the metering and isolation plates  216 ,  218  to the charging position before mixing the gel product and discharging it. 
     If the discharge point of the discharge tube  211  is known relative to the location of the object or site to be marked then the tube so directed to that location for discharge of the marking gel product. 
     If the marking apparatus is not going to be used right away, it is flushed with water to clean the product chamber  235   b,  manifold port  227 , second passage  253  and product discharge tube  211  of gel product. 
     Optionally, powdered dye can be added to the polymer powder before mixing. 
     Once discharged, the product gel has the following advantages: 
     it is visible even from the side due to its bulk, and highly visible due to the dye, visibility continuing for several hours and in even low light conditions using a fluorescent dye; 
     the gel components are easily obtained, stored and are inexpensive; 
     the apparatus is simple, requires little maintenance and easy to operate; and 
     after its useful life of several hours, the mark (gel product) degrades in an environmentally friendly manner, substantially disappearing completely in 48 hours under drying, sunlight or rain conditions.