Abstract:
A cover assembly for protecting control systems components including a base member to which control system components can be attached and a U-shaped cover having a plurality of fastening members on the top flange and a plurality of hinged members on the bottom flange. The base member has a plurality of longitudinally spaced lower slots and longitudinally spaced upper openings. The top flange of the U-shaped cover includes a plurality of fastening members sized and located to engage the longitudinally spaced upper openings in the base member. The bottom flange of the U-shaped cover includes a plurality of hinge members sized and located to engage the longitudinally spaced lower slots of the base member. The U-shaped cover can include removable lock members on the hinge members to retain the hinge members within the longitudinally spaced lower slots of the base member.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a divisional of copending application Ser. No. 09/076,178, filed on May 11, 1998. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     BACKGROUND OF THE INVENTION 
     This invention is directed to a control system for detecting the presence of packages that may accumulate on a rollerless conveyor that provides long accumulation zones in the conveyor without sacrificing accumulation density so as to simplify accumulation control zones for sensing packages that may be moved along the conveyor. 
     The prior art of accumulating packages on a conveyor wherein the package is moved along a plurality of rollers by a chain that is elevated to support the package for movement relative to frame members has means to support the package in a stationary position when not lifted by the chain for transportation to an outlet. Such a conveyor is disclosed in Wyman U.S. Pat. No. 3,930,573 of Jan. 6, 1976. 
     A variation in the prior art is disclosed in Bowman U.S. Pat. No. 3,934,707 of Jan. 27, 1976 which employs a continuously drawn belt with ways alongside the belt which are movable vertically to vary the relative vertical position between an accumulation position wherein the support surface of the ways is above the conveyor belt causing package accumulation and a package drive position wherein the support surface of the way is below the conveyor belt causing package movement. 
     The prior art includes a conveyor system of the character in Holt U.S. Pat. No. 4,149,626 of Apr. 17, 1979 in which spaced conveyor surfaces of multiple rollers are occupied by a flat link chain which is vertically movable relative to the spaced roller surfaces at selective portions to move packages. 
     Furthermore, the prior art Garro U.S. Pat. No. 5,085,311 of Feb. 4, 1992 has disclosed a belt or chain with wear surfaces along both sides of the belt or chain for conveying packages, and apparatus for displacing the belt or chain or the wear surface relative to each other to provide an in-line accumulator having a zero backline pressure. 
     BRIEF SUMMARY OF THE INVENTION 
     To overcome the prior art deficiencies it is an important object of this invention in rollerless accumulation conveyors to have a control scheme that enables the use of long accumulation zones without sacrificing accumulation density to reduce the quantity or number of zones required, thereby resulting in fewer elements in a control system. 
     Another object is to employ a control system that responds to the accumulation of packages at a discharge zone to supervise the performance of the system by delaying removal of conveyor drive contact to obtain a high package density in such zone, and also initiate final conveyor drive removal to prevent package damage once maximum density is obtained. 
     A further object of the invention is to provide photocell means to exhaust the pressure medium in a control system so as to maximize package accumulation density when the package charge rate is low, and avoiding excessive package line pressure when the charge rate is high. 
     Another object of the invention is to provide the accumulation conveyor with a control system having a location in a frame to provide a convenient working surface to perform adjustments when the protective cover for the control system is manually opened to allow for service access. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     In the drawings, 
     FIG. 1 is a schematic perspective view of a conveyor for moving different sizes of packages to be detailed hereinafter; 
     FIG. 2 is a fragmentary longitudinal plan view of the conveyor structure for moving packages seen in FIG. 1; 
     FIG. 3 is an enlarged cross section view of the conveyor structure with the package moving belt seen at line  3 — 3  in FIG. 2; 
     FIG. 4 is an enlarged cross section view of the conveyor structure when the conveyor belt is lowered as seen at line  4 — 4  in FIG. 2; 
     FIG. 5 is a fragmentary plan view of the support for the returning conveyor travel seen at line  5 — 5  in FIG. 4; 
     FIG. 6 is a schematic assembly of a control system associated with the conveyor seen in FIG. 2 with a package conveyor elevated to move packages normally along the conveyor without encountering accumulation of product. 
     FIG. 6A is the condition of the schematic control system when the conveyor belt in zone A is being lowered due to accumulation of packages; 
     FIG. 6B is condition of the schematic control system when the conveyor belt lift pads are fully exhausted of air in zone A and the control system for the belt in zone B is rendered subject to the exhaust of the initial supply of air affecting the raised position of the conveyor belt in zone B; 
     FIG. 6C is the condition of schematic control system to allow packages to begin accumulating in zone B while zone B is being lowered; 
     FIG. 6D is condition of the schematic control system when the pads supporting the conveyor belt are fully exhausted of air in zones A and B and air for belt in zone C is exhausting. 
     FIG. 6E is the condition of the schematic control system to allow packages to begin accumulating in zone C while zone C is being lowered; 
     FIG. 7 is a schematic assembly view of the control system to further illustrate the multiple alignment of a plurality of conveyor zones on which accumulation of packages has taken place; and 
     FIG. 8 is an enlarged and fragmentary schematic view of a conveyor provided with a service shelf carried at the side of the structure of the conveyor assembly so the controls employed in FIG. 4 can be accessed to effect adjustment or service of the controls schematically seen in FIGS. 6 and 7. 
     FIG. 9 is a partial perspective view of the removable cover showing the method of securing the hinge into the base member with the removable bolts. 
     Corresponding reference numerals will be used throughout the several figures of the drawings. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following detailed description illustrates the invention by way of example and not by way of limitation. This will clearly enable one skilled in the art to make and use the invention to advantage in its present best mode. 
     In the view of FIGS. 1,  2  and  3 , the conveyor  10  is seen to move different sizes of packages A or B on the surface of the rollerless bell  11  in FIG. 1 centered by side guides  12  seen in FIGS. 3 and 4. When the belt  11  is raised, as in FIG. 3, the package is lifted above stationary skid strips  13 . The section view of FIG. 3 shows the conveyor sides  14  connected by a transverse spacer  15  of which sides  14  are supported and in which the upper section  16  carries the guide supports  17  which carry the guides  12 . In addition, the spacer section  16  also carries the skid strips  13  at each side of the moving rollerless conveyor belt  11 . The return pass of that belt  11  runs over a wear control pair of strips  18  which are directed in a wave form as illustrated in FIG. 5 for the return pass of belt  11 . The strips  18  alternately connect at  19  to the sides  20  of a longitudinal channel structure and connect to each other by bolts  22 , all as indicated in FIG.  5 . 
     Further with respect to FIG. 3, the rollerless conveyor belt  11  is supported to move over the top of a support plate  23  carried by channel  24 . That top plate  23  is formed of a plastic material which provides a smooth low friction surface for the belt  11 . The underside of the channel  24  is supported on a system of spacers  25  in contact with a second channel  26 . That channel  26  rests on air expansion pad elements  27  which have upper and lower parts aligned over a down-turned deep channel  28  providing side walls  20  and a closed top surface  29  adapted to support the air expansion pad elements. The parts of pads  27  form air expansion cellular elements to provide the desired amount of vertical displacement of the conveyor belt between its recessed or lowered position and its raised or elevated position. In the position seen in FIG. 3, the belt is in its elevated position while in FIG. 4 the belt is in the lowered position due to exhausting of air from the pads  27 . 
     In the conveyor arrangement of FIG. 6 there are shown three zones of the conveyor which are related in sequence so that if a leading conveyor zone indicates that packages are accumulating and are not being downloaded from the conveyor, the next trailing conveyor zone can be prepared to slow down on package transportation or stop and accumulate packages until the package accumulation in the leading conveyor zone is conditioned to resume transportation on the moving belt or for delivery off the conveyor belt  11 . 
     In the present conveyor scheme it is to be understood that each zone in the conveyor  10  has a system of controls that are duplicated from zone to zone so that a pressure fluid valve in a leading transportation zone can signal the next trailing zone of the conveyor that packages are accumulating in the leading zone. The pressure fluid may be either a liquid or air as the pressurizing medium. What is being described in the following text will relate to the controlling device in each zone by terms that become duplicative so as to explain the control scheme being employed using air pressure. 
     For a conveyor system that has no problem of arresting or accumulating packages on a belt which can be elevated or lifted and lowered, there is shown in FIG. 6 a package discharge surface  9  having a sensor  30  to supply power to the solenoid  31  in a first valve  32  arranged to allow air from a primary air line  33  to flow from line  32 A through line  34 A to a second valve  35  which applies pressure through an internal passage seen in dotted line to hold the second valve  35  so air is able to flow into line  36  to expand the pads  27  to elevate the support plate for that zone A of the conveyor belt  11 . So long as the packages run off surface  9  to maintain power from unit  30  to the solenoid  31  of valve  32 , air from the supply line  32 A will pass through the valve  32  to the line  34 A and to the second valve  35  and to line  36  to elevate pads  27  for holding the belt  11  in FIG. 6 elevated. That second valve  35  is connected by line  37  to an orifice  38  and by line  40  to a check valve  39 . That check valve  39  is held closed by pressure in line  41 A from a third valve  41 . That third valve  41  is influenced by the position in FIG. 6 by pressure in line  42  and  43  from a first valve  44  which is connected by line  45  to the pressure line  33 . That first valve  44  is held in the position shown by current in lead  47  from a photocell  48  in zone A which has the belt  11  elevated to convey packages. 
     Continuing with FIG. 6, the first photocell  48  which is not blocked and is energizing solenoid  46  to position first valve  44  to supply air in lines  43  and  42  to a second valve  50  which is positioned by internal pressure to hold that second valve  50  to supply air into line  51  for pads  27  in zone B which holds the conveyor belt  11  elevated so that packages are free to be moved. The second valve  50  is connected by line  52  to an orifice  53  and to a check valve  54  by line  55 . Check valve  54  is held closed by pressure supplied from a third valve  56  which is set in the position of FIG. 6 by pressure in line  57  from the line  58  connected to the first valve  59  which is under the control of a photocell  64  which is not blocked in zone B. Air from the main line  33  can pass by connection  62  through first valve  59  because photocell  64  is energizing solenoid  61  to hold that first valve  59  in the position shown in FIG.  6 . 
     Continuing with FIG. 6, the second photocell  64  which is not blocked and is energizing solenoid  61  to position first valve  59  to supply air in lines  58  and  57  to a second valve  60  which is positioned by internal pressure in position to hold that second valve  60  to supply air into line  66  for pads  27  in zone C which holds the conveyor belt  11  elevated so that packages are free to be moved. The second valve  60  is connected by line  67  to an orifice  68  and to a check valve  70  by line  69 . Check valve  70  is held closed by pressure supplied from a third valve  72  which is set in the position of FIG. 6 by pressure in line  73  from the line  74  connected to the first valve  75  which is under the control of a photocell  77  which is not blocked in zone C. Air from the main line  33  can pass by connection  79  through first valve  75  because photocell  77  is energizing solenoid  76  to hold that first valve  75  in the position shown in FIG.  6 . Accordingly FIG. 6 shows free transportation of packages along its length of zone A, B and C. 
     It has been explained in FIG. 6 that there are three zones A, B and C, and each zone is associated with repetitive controls. For example, zone A is in the leading position and zone B is trailing, followed by zone C which trails zone B. Zone A discharges packages onto surface  9 , but when surface  9  is blocked or has become nonfunctional, sensor  30  removes power from solenoid  31 , allowing return spring  34  to shift first valve  32  as in FIG.  6 A. When that happens, air in line  34 A is exhausted through valve  32 , shifting quick exhaust valve  35  to gradually lower zone A pads  27  by reason of air in pads  27  being slowly exhausted through line  36  to line  37  and out orifice  38 . The fluid in line  40  is blocked at closed check valve  39  since the pressure in line  41 A is higher than that of the air exhausting from line  37 . 
     With surface  9  no longer accepting product, packages will begin to accumulate in zone A as in FIG.  6 A. Since the air in pads  27  in zone A is being exhausted slowly, packages in transit on the conveyor are able to continue to fill zone A. The size of orifice  38  can be selected based on the rate at which packages are typically being fed to the conveyor, to result in the zone accumulating full of packages before enough air exhausts from pads  27  to set packages onto skids  13 . 
     Photocell  48  has a time delay function built in which allows packages passing by in a transportation mode to be ignored. However, when packages accumulate in zone A, photocell  48  will become blocked as in FIG.  6 A. After being blocked for a preset time interval, power is removed from solenoid  46  so that valve  44  in FIG. 6B releases pressure from lines  43  and  42 , which causes valve  41  to exhaust air in line  41 A, thereby releasing check valve  39 . Any air remaining in pads  27  in zone A is able to quickly exhaust from line  40  through check valve  39  and out valve  41 . Thus the pads  27  will allow the belt  11  in zone A to lower quickly, thus avoiding an excessive build-up of package line pressure as additional packages accumulate. The uniqueness of this control scheme is that it provides a means to maximize accumulation density when the package flow rate is low, but avoids excessive package line pressure when the charge rate is high. The purpose of allowing air to escape at the orifice is to gradually lower the packages from belt  11  to skids  13  regardless of packages blocking photocell  48 . 
     The exhausting of air from lines  42  and  43  as previously described will also cause the second valve  50  to begin slowly exhausting fluid from pads  27  in zone B through line  52  and orifice  53 , but not through check valve  54  which is held closed at this time. Now zone B will accumulate packages until photocell  64  becomes blocked, as in FIG. 6C but has not timed out. After a time delay, the power to solenoid  61  will be cut off and valve  59  will shift to position in FIG.  6 D. That shift opens line  57  to exhaust air to atmosphere and shifts valve  56  which allows the check valve  54  to open line  54 A and the pads  27  in zone B will lower rapidly. Concurrently the valve  60  will open to begin exhausting the pads  27  in zone C as seen in FIG.  6 D. That action of valve  60  will allow the air in pads  27  of zone C to slowly exhaust air at orifice  68 , as check valve  70  is held closed by pressure from valve  72 . 
     Zone C will accumulate packages until the photocell  77  is blocked in FIG.  6 E. After the time delay of photocell  77  has time out as in FIG. 7 power in line  78  to solenoid valve  76  is cut off. That last event will be followed by the view of FIG. 7 which allow valve  72  to open check valve  70  which allows the pads  27  in zone C to exhaust air rapidly to lower the belt. 
     The events described taking place in zone A, B and C will continue down the conveyor  10  as long as the leading zone A of the conveyor continues to be blocked by accumulation of packages. When the surface  9  again allows passage of packages the control system will allow the zones A, B and C to progressively move packages until all zones transport packages. 
     The view of FIG. 8 illustrates a further object of the disclosure which has to do with the provision for enabling quick service to the control system when needed, all without the need to dismantle any of the structure carrying the conveyor belt and the supporting apparatus associated with it. The view of FIG. 8 is related with FIG. 3 where a side protective cover  40  has been opened for exposing the control assembly which is typical of any one of the zones shown in FIG.  6 . The controls seen in FIG. 6, are duplicated for each assembly, are carried on a plate  83  attached to the side wall  14  of the conveyor frame. The photocell  48  (zone A) is seen on the plate  83  having its connection  47  to the solenoid  46 . The principle air conduit  33  as well as the rest of the control assembly is depicted in a general way so it can be protected by the cover  40 . The cover is attached to the side  14  by a pair of hinge leafs  81  (FIG. 3) spaced along the bottom edge of the cover  40 . Each hinge leaf  81  is secured into longitudinally spaced openings  86 A by removable bolts  82  A set of retainer elements  85  are T shaped tabs adapted to be fitted into T shaped opening  86 . It is to be understood that the cover  40  can be retained by inserting the T shaped tabs  85  into the openings  86  and allowing the cover  40  to drop down so the tabs and opening gain a mutual engagement. Opening of the cover  40  requires a lifting movement to unlock the tabs  85  so the cover can be hinged out to present a work surface. 
     The package conveying system set forth in the preceding description includes a package conveying belt divided into zones in alignment, thus providing a substantially continuous path of travel through said alignment of individual supports having air pads subject to a supply of air under pressure for selectively elevating and lowering the conveying belt. A control system is operative on said conveyor belt air pads to detect movement of packages in the continuous path of travel such that should a leading zone of the belt conveyor support non-moving packages the control system has the ability to signal a trailing zone of the belt to change its positions to lower that position from a package support elevation to a belt lowering position and provide stationary means to assume the support of package so the conveyor belt movement is not interfered with and packages are supported so as to avoid trailing packages impacting on the packages in a leading zone of the conveying belt. 
     The photocells in the view of FIG. 6 are of a character that possesses a timing circuit to respond if a package holds a position to block the photocell for a time interval. Any of the convenient photocells with a solid state timing circuit can be used, such as Banner Engineering Corp. Econo-Beam Series can be selected. 
     It is also disclosed in the foregoing specification that the assembly of valves operative connected with conveyor belt offers an opportunity to simplify the control system.