Abstract:
Cool-down time is menimized by the use of a cooler having integral fins of high surface area, and the use of high-efficiency fans. Heat-up time is minimized by the low mass of the cooler, and the prevention of transmission of heat to the housing.

Description:
This technology relates to apparatus for carrying out belt-splicing operations on conveyor belts. An apparatus as described herein is portable, and can be transported to the conveyor for the purpose of effecting the splice, in situ. Also, the apparatus is suitable for in-factory or in-shop usage, to perform splices on as-manufactured belts, or to effect repairs to belts, one after another. 
     BACKGROUND 
     The technology is a development of the belt-splicing technology described in the Vortex Air-cooled Press Operating Manual, published by Shaw-Almex Industries Limited, which is incorporated herein. 
     In the new technology, the splicer includes a top platen assembly and a bottom platen assembly, which are positioned respectively over and under the to-be-spliced belt-ends. The two platens include respective pressure-surfaces, being surfaces that press directly against the splice-area, i.e against the ends of the belt that are to spliced. Both platens have their own heaters, which operate to heat the respective pressure-surfaces, and thus to heat the belt. 
     The pressure-surface of one of the platen-assemblies is capable of moving towards and away from the belt, with respect to its housing. That platen includes a pressure-bag, which, when inflated, moves the platen, and thereby applies compressive pressure to the splice. The pressure-surface in the other platen-assembly is not movable. 
     In some types of splicing, the applied heat and pressure serves to vulcanize rubber in the belt and in the splice, but in the kinds of belts that are served by the current technology, generally the belt is of, or includes, a thermoplastic material, and the heat serves to put the material into the plastic zone, such that, upon cooling, the two ends are bonded very securely. The temperatures and pressures required for vulcanization of rubber belt-ends are generally significantly higher than those for thermoplastic belts. The distinction is made between heavy-duty presses, which are robust enough to perform vulcanizations, and light-duty presses which. although less costly, are able to provide the lower temperatures and pressures as required for thermoplastic belts. The press as described herein is a light-duty press. 
     The technology is concerned with air-cooled presses, and particularly with how rapidly the pressure-surfaces of the splicer can be heated, and can be cooled after the period of heating. For rapid heating, the basic aim is to minimize the mass of the portion of the press that has to be heated, and to use efficient heaters. For rapid cooling, the aim is to provide a high flowrate of cooling air, and to provide sufficient sq.cm of hot metal exposed to the cooling air. 
     THE PRIOR ART 
     Splicing presses are known in which the press is air-cooled, and are known in which the press is water-cooled. In air-cooled presses, traditionally, only the top platen has been cooled. In water-cooled presses, it is known to cool both platens. However, designing an air-cooling system is not just a matter of simply taking a design for water-cooling, and replacing the water with air. It is the case that the shape and layout of air-cooled splicing presses do not favour the use of air to procure rapid heat-up and cool-down times. 
    
    
     
       DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       The technology will now be further described with reference to the accompanying drawings, in which: 
         FIG. 1  is a pictorial view of a belt splicer. 
         FIG. 2  is a plan view of the assembled splicer. 
         FIG. 3  is a sectioned side-elevation of the assembled splicer. 
         FIG. 4  is a sectioned end elevation showing the top and bottom housings of the splicer, shown separated. In  FIG. 4 , preparations are being made for a splicing operation. 
         FIG. 5  is an end-view of the splicer, shown with end-caps removed, and showing high-performance fans of the splicer. In  FIG. 5 , the splicing operation is under way. 
         FIG. 6  is a pictorial view of one end of the splicer, with end-caps removed. 
         FIG. 7  is the same view as  FIG. 1 , but with a top-housing removed. 
         FIG. 8  is the same view as  FIG. 7 , but with a pressure-bag of the apparatus removed, and with a cover removed. 
         FIG. 9  is a cross-section of a thermal tray-assembly of the splicer. (Note: the height dimension has been doubled in  FIG. 9 , for clarity of detail.) 
         FIG. 10  is a pictorial view of the thermal tray-assembly. 
         FIG. 11  is an exploded view of the several components and layers of the tray-assembly of  FIG. 10 . 
         FIG. 12  is a pictorial view of an assembled controller tray-assembly of the splicer. 
         FIG. 13  is a pictorial view of an assembled inflator tray-assembly of the splicer (seen from underneath). 
     
    
    
     The belt splicer  20  shown in the drawings includes a top housing  21  and a bottom housing  22 . Also, a top left end-cap  23 , a top right end-cap  24 , a bottom-left end-cap  25 , and a bottom-right end-cap  26 . The housings  21 , 22  are aluminum extrusions. The top end-caps  23 , 24  are bolted to threaded sockets formed in the top housing extrusion  21 —likewise for the bottom components. 
     In  FIG. 4 , the splicer  20  is being prepared for a splicing operation. The bottom housing  22  is resting on a firm support. The top-housing  21  is separated from the bottom-housing at this point. The ends of the belt  27 A, 27 B to be spliced are laid over a bottom platen-assembly  28 , and are clamped in place with clamping bars  29  and handles  30 . (Generally, with the kind of splicing technology employed herein, the belt-ends are form-punched into tapered fingers, which interlock at the splice area.) An upward-facing top surface  31  of the bottom platen-assembly  28  is in direct contact with the belt  27 . 
     As shown in  FIG. 5 , the top housing  21 , with a top-platen-assembly  32  attached, is lowered down onto the belt. A downward-facing bottom surface  33  of the top platen-assembly  32  is in direct contact with the belt. The operators secure the top housing  21  to the bottom housing  22  by means of screw-clamps  34  located in the ends of the splicer. 
     The electrical connections having been made, and the safety checklist having been completed, now the splicing operation can be carried out.  FIG. 5  shows the splicer in the assembled condition. A tether-cable  35  ( FIGS. 2,3 ) provides electrical-power and sensor-signal connection between the housings. A cord (not shown) connects the splicer to e.g 13-amp, 110-volt-AC mains. 
     A pressure-bag  36  of the splicer  20  is inflated to the required target pressure, to apply compressive pressure to the splice area of the belt. Heaters in the splicer are switched on, and during the warm-up phase (which takes a few minutes) the belt is brought up to the target hot-temperature. When the hot-temperature is reached, the heaters are operated to maintain the hot-temperature during a heat-soak phase (which takes another few minutes). The pressure-bag  36  remains inflated during the heat-soak phase. After the heat-soak is completed, the heaters are switched off, and the air-blowers are switched on during the cool-down phase (which takes a further few minutes). The pressure-bag remains inflated also during the cool-down phase. 
     After the belt has cooled down to the target cool-temperature, now the operators deflate the pressure-bag. The operators unfasten the top housing  21  from the bottom housing  23 , and remove both housings from the now-spliced belt. 
     The present technology is aimed at reducing the length of the warm-up phase, and reducing the length of the cool-down phase, and thus reducing the overall cycle time of the splicing operation. 
       FIG. 7  is a view of the splicer  20  with the top housing  21  removed. The pressure-bag  36  is connected by a hosepipe to an electrically-powered air-compressor  37 , which can be operated to inflate the pressure-bag. (It will be understood that the bag  36  is blocked from inflating upwards when pressurized because the top surface of the bag  36  abuts against a surface  38  ( FIG. 4 ) of the top housing  21 .) 
     In  FIG. 8 , the pressure-bag  36  has also been removed, exposing the cooler  39 . The cooler is formed from a unitary block of aluminum, in which the fins  40  have been formed by machining away the spaces  41  between the fins  40 . 
     As shown in  FIG. 9 , the cooler  39  is a monolith comprising a base-plate  42  and the several upstanding fins  40 . The cooler also includes side-walls  43 . A cover  44  of insulating plastic (phenolic) material is secured into a recess in the side-walls. (The cover  44  has been removed in  FIG. 7 .) 
       FIG. 9  shows the several components of a thermal-tray assembly  45 . The thermal-tray assembly  45  is shown pictorially in  FIG. 10 . The components of the thermal-tray assembly are shown exploded in  FIG. 11 . 
     The assembly  45  is based on a sheet metal (stainless steel) tray  46 , having folded-up sidewalls  47  and folded-in lips  48  which form a partial roof. (The bottom or undersurface of the stainless steel tray  46  is the downwards facing bottom surface  33  of the top-platen assembly  32 .) Next up from the floor of the tray  46  is a layer of (electrically conductive) graphite  49 . 
     Above that is the electrical heating pad  50 . Electrically-insulating layers or films  51  of Kapton® are placed above and below the heating pad  50 , in case of an electrical fault in the pad. (Though highly electrically-insulative, the Kapton® films  51  offer barely any resistance to transmission of heat.) The films  51  are not shown in  FIG. 9 . 
     The cooler  39  rests on top of the heating pad  50  (actually on top of the upper Kapton® film  51 ). As mentioned, the plastic cover  44  is secured (with screws) to the side-walls  43  of the cooler. The cover  44  lies in contact with the tips of the fins  40 . Thus, when the pressure-bag  36  is inflated, the cover is pressed down against the fins  40 , whereby the fins are transmitting the pressure-force to the belt. 
     On top of the cover  44  is a layer  52  of plastic heat-insulation material. The cooler  39  of course becomes hot when the heating pad is switched on, and the insulating layer  52  protects the pressure-bag from that heat. 
       FIG. 10  is a view of the assembled layers, which are arranged to be slidable into the cavity created by the shape of the stainless steel tray  46 . The height of the stack of layers (which includes the cooler  39 ) is such that, when the stack has been inserted into the cavity, the fit is tight enough to retain the stack therein. 
       FIGS. 9,10,11  show the top thermal-tray assembly. The bottom thermal-tray assembly  53  is a mirror-image of the top thermal-tray assembly. 
     The graphite layer  49  in the thermal-tray assemblies provides heat-conductive compliance and conformance, and is aimed at eliminating differences and gradients of temperature over the bottom-surface of the floor of the stainless steel tray—being the surface  33  of the splicer that directly contacts the belt being spliced. (In fact, often, operators place a thin sheet of a non-stick plastic material between the bottom-surface  33  and the belt, to prevent sticking. The above word “directly” should be construed to include the possible presence of such sheet.) 
       FIG. 12  shows a controller sub-tray assembly  59 . This assembly carries control components and connectors, for receiving signals from temperature and other sensors, and a processor for automatically controlling the phases and operations of the splicer in response to the signals. This tray slides into the bottom housing  22 . 
       FIG. 13  shows an inflation sub-tray assembly  60 , which carries the air compressor  37  for inflating the pressure-bag  38 , and a tube or hose for connecting to same. This tray slides into the top housing  21 . In fact, the slideways  62  for the inflation-tray assembly are in the roof of the top housing, and the components are mounted underneath the tray. 
     Cooling of the belt is done by blowing cooling air through the spaces  41  between the fins  40  of the top and bottom coolers  39 . The air-blowers, or fans, preferably should have the following properties. 
     In the splicer  20 , there are two top fans and two bottom fans. The example splicer has the capacity to splice belts of 1.5 meters width. (Smaller splicers can be provided with one top fan and one bottom fan. The top fan by itself, or the top fans together, have the capability to move air at a flowrate of at least three hundred liters per minute, multiplied by the maximum belt width (MBW) of the particular splicer. The bottom fan or fans should have a similar performance. 
     The fans should be highly efficient. Preferably, each fan should have the capability to deliver the said air-flowrate against a pressure head of twenty psi centimeters of water, upon being supplied with half a kilowatt of electricity or less. 
     The fans should also be compact, given that space is at a tight premium inside the profiles of the top and bottom housings. The housing of the fan has the basically-cylindrical form arising from housing an electric motor which is coaxially in-line with the fan-blades, and includes a volute-chamber and a tangential outlet-tube for collecting the pressurized air and conveying same out of the fan. That being so, the fan should be small enough to fit in a cubic box six cm by six cm by six cm. (It should be noted that the length of the outlet-tube of the fan is not included in this size stipulation—because the length of the outlet-tube is determined by criteria other than the compactness of the fan housing and the fan unit.) 
     The actual fan (four of them) used in the exemplary splicer  20 , as described herein, was obtained from Micronel AG, VH-8307 Tagelswangen, Switzerland (www.micronel.ch), under the product name Miniature Radial Blower, catalog product designation U51DL-024KK-4, and was found to be satisfactory from the standpoints of flowrate created, energy efficiency, and compactness. 
     The locations of the top fans are shown in  FIGS. 5,6,7,8 , and one of the bottom fans in  FIG. 6 . Each fan is attached to the cover  44  of the cooler. A length of rigid tubing  55  is cemented into a hole in the cover plate  44 . A length of semi-flexible tubing  56  is a tight fit over a length of rigid tubing  55 . The outlet-tube of the fan is of such diameter that the outlet-tube can be inserted into the length of semi-flexible tubing. This manner of mounting the fan is simple and yet very secure. No other mounting structure is needed, other than to push the outlet-tube of the fan into the tubing. 
     The cooler is so arranged that air from the fans is received into the spaces between the fins of the cooler, and is directed by the layout of the top fins lengthwise along the cooler. The fins are arranged to direct heated air (i.e air that has performed its cooling function) through openings in the side-walls of the metal-tray  46 . 
     The cooler should be structured so that the aggregate surface area of the metal of the top base-plate and top fins that is exposed to fan-blown cooling air during the cool-down phase is 2500 sq.cm per meter length of the base-plate, or more. In the example, the exposed area was 3800 sq.cm per meter length. In the example, the fins protruded ten mm out from the base-plate. 
     From the standpoint of rapid heat-up, the components that have to be heated should be kept to a minimum. The cooler  39  has to be heated, and also the metal tray  46 . And the metal tray is physically exposed, so it has to be chunky (in the example, the sheet metal plate is one mm thick.) Thus, the heat capacity of the steel tray  46  is considerable. The mass of the cooler is small, which is beneficial (not only for portability of the splicer) but because the lower the thermal capacity of the cooler, the quicker it warms up, and the less energy it takes. The heat-up phase in traditional splicers has taken e.g fifteen or twenty minutes; in the example, that time can be reduced to e.g four or five minutes. 
     The mass of the cooler preferably should be no more than 1½ kilograms per meter length of the base-plate. In the example, the mass of the aluminum cooler was one kg per meter length. 
     The two main factors in reducing heat-up time are the low thermal capacity of the components that have to be heated, and also because precautions have been taken, in the new design, to ensure that as little heat as possible (and preferably none) of the heat from the heater is wasted by heating up the housings. Thus, in the present design, the components that have to be heated do not touch the housing, and therefore shed no, or only minimal, heat to the housing. 
     During the cool-down phase, the cooler has to conduct heat rapidly away from the belt. The heat from the belt has to travel through the metal of the tray  46 , through the graphite layer  49 , and through the heater pad  50 , before reaching the underside of the base-plate  42  of the cooler, and then the heat must pass through the base-plate before it can be dissipated into the air passing through the spaces  41  between the fins  40 . These barriers are the reason why rapid cooling is difficult to achieve, in an air-cooled press. In conventional belt splicers, the cool-down phase can occupy e.g fifteen or twenty minutes; that time has been reduced to about four minutes in the exemplary design. 
     KAPTON is a registered trademark of E I du Pont de Nemours And Company. 
     The scope of the patent protection sought herein is defined by the accompanying claims. The apparatuses and procedures shown in the accompanying drawings and described herein are examples. 
     The numerals used in the drawings are listed as:
       20  belt splicer     21  top housing     22  bottom housing     23  top left end cap     24  top right end cap     25  bottom left end cap     26  bottom right end cap     27 A, 27 B ends of belt to be spliced     28  bottom platen assembly     29  clamping bars     30  clamping handles     31  upward-facing top surface of bottom-platen     32  top platen assembly     33  downward-facing bottom surface of top-platen     34  screw clamps     35  tether cable     36  pressure-bag     37  air compressor     38  air-bag surface of top housing     39  aluminum cooler     40  fins of cooler     41  spaces between fins     42  base-plate of cooler     43  side-walls of cooler     44  plastic cover of cooler     45  thermal-tray assembly     46  sheet metal tray     47  folded-up side-walls     48  folded-in lips     49  layer of graphite     50  electrical heating pad     51  films of Kapton®     52  layer of heat-insulation material     53  bottom thermal-tray assembly     54  air-blower/fan     55  rigid tubing, fixed to cover  44       56  semi-flexible tubing     57  outlet tube of the fan     59  controller sub-tray assembly     60  inflation sub-tray assembly     62  slideways in top housing     63  exhaust openings in the sidewalls of the tray