EP0152960B1 - Rotatable film wrapping apparatus and process for unitizing a load with a compressive overwrap - Google Patents
Rotatable film wrapping apparatus and process for unitizing a load with a compressive overwrap Download PDFInfo
- Publication number
- EP0152960B1 EP0152960B1 EP85101960A EP85101960A EP0152960B1 EP 0152960 B1 EP0152960 B1 EP 0152960B1 EP 85101960 A EP85101960 A EP 85101960A EP 85101960 A EP85101960 A EP 85101960A EP 0152960 B1 EP0152960 B1 EP 0152960B1
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- European Patent Office
- Prior art keywords
- film web
- load
- roller
- elongation
- downstream
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- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65B—MACHINES, APPARATUS OR DEVICES FOR, OR METHODS OF, PACKAGING ARTICLES OR MATERIALS; UNPACKING
- B65B11/00—Wrapping, e.g. partially or wholly enclosing, articles or quantities of material, in strips, sheets or blanks, of flexible material
- B65B11/008—Wrapping, e.g. partially or wholly enclosing, articles or quantities of material, in strips, sheets or blanks, of flexible material by webs revolving around articles moved along the axis of revolution
Definitions
- the present invention generally relates to packaging and more particularly is directed to a rotating stretch wrapping apparatus for making unitary packages which hold a plurality of components, each package containing a load wrapped in a web of stretched film.
- the present invention specifically relates to an apparatus and a process for wrapping a film web around a load with a cross section which causes variations in demand rate for the film web during wrapping, said apparatus comprising a frame and dispenser means mounted on the frame for revolving around the load, and having at least one feeding roller for dispensing the film web, while said process comprising revolving a film web dispenser around the load and dispensing the film web from at least one roller in the film web dispenser to wrap the load.
- United States Patent No. 4,317,322, assigned to Lantech, Inc. disclose a pre-stretch film elongation system mounted adjacent a film roll and rotated about a stationary load.
- the pre-stretch system which is mounted on the rotating ring includes an upstream roller and a downstream roller across which the film web successively passes.
- the two rollers are coupled by gears, belts, or the like, which force a constant ratio of velocity between the rollers.
- Film is drawn from the film roll and across each of the rollers by relative rotation of the ring around the load.
- the fixed speed ratio between the upstream and downstream rollers; in which the downstream roller moves more quickly than the upstream roller, causes substantial and constant stretching between the rollers of the web.
- the substantial changes in demand speed are transmitted directly from the load back through the web to the pre-stretch device, so that the supply speed of the film moving across the downstream roller to the load changes accordingly.
- the entire force exerted between the rollers is applied to the rollers by film being wrapped about the load, and that pre-stretch device inertia and the elasticity of the film web between the downstream roller and the load causes a phase delay or lag in supply speed changes.
- any hole in the web such as those which commonly occur at web imperfections or gauge variations, causes a weakening between the load and the pre-stretch mechanism, thus slowing or stopping the pre-stretch mechanism. The hole is then elongated and enlarged by the growing difference between supply and demand speeds, finally breaking the film web and interrupting the wrapping procedure.
- the second characteristic is that, in prior art wrapping systems, locking in at load edges occurred precisely at the point where the film web experienced a minimum of force and elongation, having partly retracted and recovered from a prior maximum force/elongation point, thereby locking in the same minimum characteristics. Since a maximum force was also experienced during the wrapping of each load side, an attempt to raise overall force in order to raise the minimum point will also raise the maximum point and increase the risk of exceeding the failure point for the film web. An attempt to lower overall force for delicate loads will reduce the minimum point and risk zero containment of the load. Hence, the .
- DE-A-2,256,708 describes a wrapping apparatus wherein the supply roller is guided a path of simular configuration as the peripheral shape of the load. No means are provided for compensation of inertia forces or taking care of the above discussed characteristics.
- the apparatus and process should avoid control of the at least one feeding roller or the pre-stretch system through the film web itself, so that the feeding roller or the pre-stretch system will not decelerate when holes develop in the film web. Thus the risk of hole expansion and film failure will be minimized.
- the apparatus of the invention is therefore characterized by supply speed control means coupled to the roller through a mechanism other than the film web for increasing and decreasing the rotation speed of the roller, said supply speed control means comprising means defining a predetermined model substantially approximating the cross-sectional configuration of the load for rotatably controlling the speed of the roller in response to input from said load model, said input being independent of both actual sensed variations in the tension of the film web and actual sensed variations in the demand rate for the film web downstream of the roller, said supply control means dispensing the film web from the roller at a controlled variable supply speed according to said load model input independent of the sensed variations in the tension of the film web and sensed variations in the demand rate for the film web downstream of the roller, while the process of the invention is characterized by forming a predetermined model substantially approximating the cross-sectional configuration of the load; and controlling the rotation speed of the roller by rotatably controlling the speed of the roller through a mechanism other than the film web in response to input from said load model, said input being independent of both actual
- the present invention is directed toward an apparatus and process for applying stretchable plastic film to loads using a feed roller, preferably a pre-stretch mechanism which is driven and controlled independently of the web tension to minimize variations in the force exerted on the film web at load edges by varying the film web supply speed.
- Film web is drawn to the load at a demand speed which varies during rotation of a film roll about a load.
- the supply speed changes required to minimize web elongation and containment force changes at load edges are transmitted to the feed roller or the pre-stretch mechanism by a supply speed control mechanism using a predetermined model of the load, which permits higher levels of stretch, faster payout speeds, and use of less uniform film than were previously thought possible.
- the present invention reduces the likelihood of unexpected web breakage during wrapping, increases throughput and conserves film by establishing load containment with fewer web layers.
- a series of loads are fed into a rotating wrapping apparatus having preferably a film web pre-stretch mechanism and elongation drive mechanism. Each load is covered by a plurality of layers of stretched film to form a unitary package.
- the pre-stretch mechanism is mounted on a rotating ring through which a load travels for encirclement by stretched film web.
- the supply speed control mechanism is mounted adjacent the rotating ring. Energy is delivered to the pre-stretch mechanism during rotation of the rotating ring by way of a power pulley, cam follower or the like mounted to the pre-stretch mechanism.
- the power pulley engages the supply speed control mechanism and revolves at a varying rate due to friction thereon.
- the power pulley then transfers its energy and speed to the film pre-stretch mechanism.
- the pre-stretch mechanism is thus operated at a varying speed and supplied with the force required to stretch the film by the supply speed control mechanism.
- the invention provides a novel and useful improvement over the prior art rotating wrapping machines, both those utilizing brake stretching systems and those utilizing coupled roller stretching systems. This is advantageously accomplished without the need to transfer electrical power or control signals from a stationary source to devices such as brakes or motors on the rotating ring.
- yield point designates a range or region on the stress-strain curve, rather than a dimensionless point.
- Limitations of friction-based constant force devices prevent current stretch wrap applications from achieving the higher levels of containment force and ultimate strength available in the foremost plastic films. Achieving the higher elongation levels with the invention allows wrapping with fewer revolutions of film yet maintains equivalent holding power. These higher levels of stretch not only allow fewer revolutions of film but also permit wrapping with less film by weight for each revolution.
- the present invention allows at least double the practical level of elongation currently experienced with prior art "brake” systems. This gives higher containment forces and/or lower film costs to the end user.
- the invention allows for more precise control of web speeds and forces thereby achieving greater cost efficiency from high yield films, along with higher film strength or modulus achieved at higher levels of elongation.
- the novel construction of the invention provides for isolation of the pre-stretch mechanism from stretch forces which eliminates premature film failure from development and elongation of holes at web imperfections.
- This construction eliminates friction brakes and the problems of those brakes such as speed variation, break away from stop position, temperature variation, wear and operator control meddling.
- the present invention provides a unique apparatus and process with an elongation mechanism driven to apply uniform film web containment across every side of the load.
- the film is preferably stretched beyond its yield point as it is accelerated.
- the acceleration force is provided by the supply speed control mechanism, which also precisely varies the web supply speed to lock in predetermined elongation and containment force on the load.
- FIG. 1 The best mode and preferred embodiment of the present invention is disclosed in Figures 1 through 3, and comprises a ring wrapping apparatus 30 comprising a feed conveyor 32, a wrap and load conveyor assembly 34, a film dispensing mechanism 36 with a take-off conveyor 20.
- a plurality of units 22 forming a load 24 have been loaded in a stacked relationship on an infeed conveyor assembly 32 by either manual or mechanical means. It should be noted that the load, depending on its nature and composition, may or may not require spacing.
- the loading device 31 is schematically shown and may be one of a number of types of stacking or placing devices which are well known in the art to place a stack of cartons or materials into designated areas.
- containment force refers to force applied to a load by film web surrounding the load when wrapping is completed
- wrapping force refers to force applied by film web extending from the wrapping system to the load during wrapping. Wrapping force is, of course, applied equally and oppositely to the film web and to the load simultaneously.
- the load 24 is placed on an infeed conveyor 32 which is comprised of an endless belt 26 mounted on frame support 28.
- An alternate embodiment of the infeed conveyor could take the form of a hydraulic or pneumatic pushing device (not shown) which can be used to engage each load 24 with a platen to push the load into the wrapping area.
- the conveyor embodiment is preferred and the belts of the conveyor of the present invention are preferably textured so that they have a high coefficient of friction.
- the conveyor belt 26 as seen in Figure 1 is mounted on rollers 29 which are rotatably journalled by suitable bearing means in brackets which are secured to the frame support 28.
- the infeed conveyor 32 carries the loads 24 onto a wrapping station 41 comprising film dispensing apparatus 36, and wrapping conveyor assembly 34.
- the preferred embodiment and best mode of the invention comprises a frame 42 on which a steel "donut" or ring-shaped film support member 44 is rotatably mounted and supported on three planes by guide rollers 46.
- the film support member can be constructed of aluminum.
- a plurality of guide rollers 46 project inward from the frame 42 on arms 47 and mounting plates 48 to engage the ring-shaped member so that it can be driven in a predetermined path.
- a friction drive wheel 49 is positioned adjacent the ring member 44 at its base and engages the member 44 to rotate the member 44 within the guide wheel rolling area.
- the friction drive wheel 49 is driven by a motor 50 having a shaft which is suitably connected with a drive reducer 52.
- a material roll dispensing shaft 54 is rotatably secured to the ring member 44 for rotation on its axis and is adapted to receive and hold a roll of film material 56.
- An important aspect of film wrapping apparatus performance is that the elongation and containment force exerted by any one layer of film applied across any given side of a load is not influenced by the characteristics of the same layer of film wrapped to either a prior side or a subsequent side of the load.
- Load edges are barriers preventing film slippage which would otherwise alter film elongation and containment force.
- film elongation and containment force are locked in for a given load side when the film encounters the edge at the end of the side.
- FIGs 7 through 9 A schematic representation of film demand rate at load edges is shown in Figures 7 through 9 in which a pre-stretch mechanism 70 is rotated in the direction indicated by the arrow D around a center point Y at a constant angular velocity to wrap a representative rectangular load 24.
- the film web 58 has just completed wrapping a long side of the load and has encountered corner X.
- the film web 58 passes on a straight line from pre-stretch mechanism 70 across the long face of the load.
- the line of film web 58 therefore forms a right angle with the line segment A extending from the rotation center Y to the tangent point T.
- the rate of demand for film web by the load 24 during wrapping can be computed by treating the line segment A as the effective wrapping radius of a circle J to which film 58 is tangent at point T. It can readily be appreciated that the rate of demand for film will increase as the effective wrapping radius increases, under constant angular rotation of the pre-stretch mechanism 70.
- film web is demanded by the load at a rate which varies but is always at a minimum when a side is completely wrapped and a corner is encountered. This swing from minimum to maximum and back occurs once for each load side, or four times per revolution for a load of rectangular cross-section.
- film web 58 is dispensed from pre-stretch mechanism 70 at a constant rate, the net film web acceleration and force will follow the same pattern of variation as the demand rate. This is illustrated in Figure 5, in which a curve 190 shows the varying wrapping force experienced by the load as well as the film web between the load and the downstream roller of a typical prior art pre-stretch system.
- Each minimum point 196 of the curve 190 occurs precisely when a corner is wrapped at the completion of wrapping a side of a load.
- Each maximum point 198 of curve 190 occurs after the minimum point 196 occurs and before the film web characteristics are locked in for the side when a subsequent corner is encountered.
- the final level of force 196 is significantly less than the maximum force level 198, during the prior art wrapping of any side of the load.
- a general stress-strain curve 140 is shown which illustrates the relationship between elongation and force for a generalized film web composition.
- the curve region indicated at 141 is generally known as the elastic limit or yield point for the material. If, starting with no elongation; the material is stretched by a force which is sufficient to elongate the material no further than the region indicated at 141, then when the force is removed the material will return along the same curve 140 back to zero elongation at zero force. However, if force is exerted to carry the elongation of the film web beyond the region indicated at 141, such as to the point indicated at 148, then the film web has exceeded its elastic limit and reaches elongation point 248.
- the preferred embodiment of the present invention advantageously exerts a wrapping force to a load as well as on the film web between the load and the pre-stretch mechanism which approaches curve 300 illustrated in Figure 10, which is a flat line.
- curve 300 illustrated in Figure 10 which is a flat line.
- the force curve can easily be elevated to lock in elongation and force to the load at a point 148 on curve 140 of Figure 6 above the elastic limit region 141. It can be appreciated that, for a load wrapped with the present invention, extreme load circumference reduction would have to occur before containment force were relaxed to the point 160 illustrated in Figure 6.
- the force curve can also be easily depressed to wrap delicate loads at low wrapping force without risk of a variation eliminating containment force completely.
- Typical films which can be used in the stretch wrapping apparatus are EVA copolymer films with a high EVA content such as the films manufactured by Consolidated Thermoplastics "RS-50", Bemis “Super-Tough”, and PPD “Stay-Tight” films.
- PVC films such as Borden Resinite "PS-26” can be used in the invention along with premium films such as Mobil-X, Presto premium and St. Regis which utilize a low pressure polymerization process resin manufactured by Union Carbide and Dow Chemical Company. This resin, called linear low density polyethylene, has significantly different stretch characteristics than previous stretch films. These characteristics allow the film to withstand the high stress of extreme elongation without tearing during wrapping of the load.
- film, film material and film web are used interchangeably throughout the specification.
- supply speed control mechanism 90 comprises a pulley frame 39 parallel to ring member 44 fixed to frame 42, and a plurality of double-sheave pulleys 62 rotably mounted on shafts 63 journalled to frame 39.
- the frame 39 comprises horizontal members 172 defining lengthwise slots 173, and vertical members 174 defining lengthwise slots 175.
- Bolts 176 are placed through slots 173 and 175 to adjustably retain members 172 and 174 in a particular orientation as will be set forth more fully below.
- Shafts 63 may be threaded at a frame end and locked with threaded nuts into a particular spacing in slots 174.
- the shafts 63 are placed so that they define corners of a polygon having an aspect ratio equal to that of a load cross-section.
- the term "aspect ratio equal” here means identical length ratios of adjacent sides and identical edge angles therebetween. Two polygons having equal side ratios and equal edge angles are said to have identical aspect ratios even though one may enclose greater area than another.
- the illustrated form of frame 39 permits easy adjustment to accomodate variation in load cross-section. Although four pulleys 62 and a rectangular frame 39 are shown in the drawings, this number is exemplary only and any appropriate number of pulleys and sides may be utilized.
- a power belt 64 passes around an outer sheave 65 of each pulley 62, and a drive belt 66 passes around an inner sheave 67 of each pulley 62.
- Belts 64 and 66 may comprise chains, belts or other well-known equivalents. If chains are utilized then the sheaves are replaced by coaxial gears.
- a power pulley 68 mounted on power axle 61 across ring member 44 engages belt 64 so that rotation of ring member 44 relative to belt 64 causes pulley 68 and axle 61 to rotate in an opposite direction at a speed which varies in each revolution of ring member 44 due to passage of belt 64 around pulleys 62.
- Drive belt 66 also engages drive pulley 78 mounted to a rotating output shaft of drive motor 81, so that belt 64 is driven by motor 81 and the speed of motor 81 may be adjusted to increase or decrease the rate of relative rotation between belt 64 and ring member 44 without affecting the rotation rate of ring member 44 relative to the load.
- the film web is drawn from roll 56 through a pre-stretching or elongation mechanism 70 and is tucked or fastened underneath or held adjacent the load.
- the pre-stretching mechanism ,70 which is best seen in Figure 2, comprises connected roller members 72 and 74 which are rotatably mounted respectively on shafts 73 and 75 which are in turn journalled to a housing 76.
- the housing 76 is mounted to and across the plane of the ring member 44.
- Gears 77 and 79 are mounted respectively to shafts 73 and 75, and mesh together and are driven by the supply speed control mechanism 90 as the film web engages the rubber roller surfaces.
- the film web passes first across the upstream roller 72 and then across the downstream roller 74 as it is pulled from film roll 56 to the load 24, and the gears 77 and 79 operate as an elongation control to rotate downstream roller 74 faster than the upstream roller 72, causing the film to be accelerated and stretched in a narrow space 80 between the two rollers.
- the ratio of the gear 77 to the gear 79 preferably ranges from 3:2 to 4:1, so that downstream roller 74 rotates faster than upstream roller 72 by a ratio ranging from 3:2 to 4:1. While a two-roller elongation system is preferred, it is an obvious modification to utilize any number of rollers therein, including a single roller pulling against a restrained film roll.
- Film roll 56 can be urged against upstream roller 72 in any well-known conventional manner such as by a coil spring (not shown), which maintains friction of upstream roller 72 and film roll 56 as film payout reduces the diameter of film roll 56. Contact of roller 72 and roll 56 prevents uncontrolled payout of film web due to momentum of film roll 56 upon deceleration of roller 72 during normal operation.
- a coil spring not shown
- a pivoting collar 83 may be placed around upstream roller shaft 73, and a countereight 85 and contact frame 84 may be mounted at angles to the collar 83.
- a contact roller shaft 51 is rotatably journalled to frame 84.
- Contact roller 57 is mounted to an end of shaft 51 adjacent roll 56 for engagement with roll 56.
- Contact roller pulley 53 is mounted to an end of shaft 51 opposite roller 57.
- An upstream pulley 55 is mounted to shaft 73. Pulleys 53 and 55 are engaged by pulley belt 59, and the ratio of pulley sizes and the circumference of roller 57 are chosen such that the linear surface speed of roller 57 is slightly less than the linear speed of upstream roller 72.
- a coil spring 86 is coupled to frame 84 and housing 76 so as to constantly urge contact roller 57 against the surface of film roll 56 which decreases in radius as film web 58 is paid out during wrapping.
- Spring 86 forces roller 57 to maintain contact with the surface of roller 56 during rotation of ring member 44.
- Counterweight 85 exerts leverage on frame 84 to compensate for the effect of the force of gravity on roller 57 as ring member 44 rotates. Therefore, friction between roller 57 and film roll 56 will be maintained, and pay out speed of film web 58 from roll 56 will accelerate and decelerate precisely to match speed changes of the elongation system.
- Shaft 61 extends through housing 76 a distance at least equal to the distance between rotary ring 44 and pulleys 62 for interaction with supply speed control means 90.
- a power pulley 68 is mounted on the end of shaft 61 so as to engage belt 64 as ring member 44 rotates. Contact of pulley 68 and belt 64 is maintained throughout the revolution of ring member 44, and tension on belt 64 is mintained by pressure of tensioner roller 69, which is spring-loaded in any well known conventional manner.
- Belts 64 and 66 are preferably made of rubber or another material with resilience and a high coefficient of friction against the material of pulleys 62 and 68, which is preferably metal.
- An end of shaft 61 opposite that to which pulley 68 is mounted extends beyond the housing 76, and transfer pulley 21 is mounted thereto.
- An end of downstream roller shaft 75 likewise extends beyond the side of housing 76 where pulley 21 is mounted, and downstream roller pulley 25 is mounted to it.
- Transfer belt 23 engages pulleys 21 and 25, so that downstream roller 74 is driven to rotate at a speed proportional to that of pulley 68 via shaft 61, pulley 21, belt 23 and pulley 25.
- the film supply rate from the pre-stretch mechanism 70 varies precisely as the film demand rate to the load varies, so that the net acceleration difference between the rates is constant.
- the film supply rate is controlled by the rate of passage of belt 64 across pulley 68, which varies as belt 64 encounters each pulley corresponding to a load corner. Because the load 24 and the pulleys 62 share a common aspect ratio, the speed of belt 64 varies precisely as shown in Figure 5 for the same reasons, illustrated in figures 7 through 9, that the film demand rate varies along the curve shown in Figure 5.
- the portion of belt 64 trailing from pulley 68 is demanded or pulled away by pulleys 62 at a rate which varies according to the changing effective wrapping radius around pulleys 62, just as the film is pulled away from pre-stretch mechanism 70 to the load 24 at a rate which varies according to the changing effective wrapping radius around the load.
- the film supply rate changes from a minimum to a maximum and back four times per dispenser revolution about a load of rectangular cross-section, but other configurations of pulleys 62 can be used with equal effectiveness for loads of other cross-sectional shapes.
- the pulleys 62 and belt 64 of supply speed control means 90 serve as a predetermined model of the load 24 which controls the output rate of pre-stretch mechanism 70 without reliance on feedback through film web between roller 74 and the load. So long as the angles and ratios of side lengths remain equal for the pulley 62 area and the load cross-section, the demand rate for belt 64 will follow the load demand rate for film 58.
- FIG. 12 An alternate embodiment of the supply speed control mechanism designated 95 is illustrated in figures 12 through 14.
- the belt 65, motor 81, pulley 78, pulley 68, pulley 63, frame 39, pulleys 62, and tension idler 69 are omitted.
- ring or track 60 is configured as a solid surface having a series of consecutive areas of greater or lesser radius, which may be considered as cam bumps or depressions respectively.
- the number and spacing of depressions 97 corresponds to the number and spacings of load vertices for purposes which will become apparent below.
- a power column 182 is mounted to power axle collar 181.
- the column 182 extends beyond the housing 76, and a second collar 183 is mounted at an end of column 182 remote from collar 181.
- An axle 184 passes through collar 183 and extends to the plane of ring 60.
- a contact roller 185 is mounted to axle 184.
- a tensioned coil spring 189 extends from housing 76 to collar 183 in order to urge roller 185 against the surface of ring 60 during rotation of ring 44.
- pulley 186 is mounted to the axle 184.
- a second pulley 187 is mounted to power axle 61, and a belt 188 engages pulleys 186 and 187.
- contact roller 185 is driven to rotate by friction against ring 60.
- the rotation of contact roller 185 in turn rotates axle 184, pulley 186, belt 188, pulley 187 and power axle 61.
- Power axle 61 acts to drive elongation amd dispensation of film web 58 as described above for the preferred embodiment.
- the rate of rotation of contact roller 185 increases across each raised portion of ring 60 and decreases in each depression of ring 60, with the column 182 acting as a cam follower by pivoting about power axle 61 to maintain contact between ring 60 and contact roller 185.
- Each depression 97 of ring 60 is positioned so as to reduce contact roller 185 speed and thereby minimize the supply speed V, of film web across the downstream roller 74 precisely when a corresponding edge 89 of the load is approached by the film web 58.
- the depth of each depression 97 is sufficient to maintain the difference between the takeup speed V2 and the supply speed V, to minimize the force and elongation variations as each load edge is encountered by film web 58.
- the roller 185 encounters a plateau on ring 60, with a corresponding greater linear circumferential distance per unit of angular rotation of ring 44. The linear speed of roller 185 will increase, correspondingly increasing the supply speed V, of film web 58 leaving the downstream roller 74.
- the alternate embodiment achieves the desired effect of uniform acceleration, elongation and force at each load edge to lock in containment on each side of the load.
- the alternate embodiment decelerates and accelerates the speed V, of film web 58 four times per revolution of the system about a load of rectangular crosssection, but other patterns of depressions 97 could be used with equal effectiveness for loads of other cross-sections.
- the ring 60 comprises a predetermined model of the load which controls the output rate of pre-stretch mechanism 70 without reliance on feedback through film web between roller 74 and the load.
- the wrapping conveyor assembly 34 as best seen in Figure 14 comprises two stacked conveyors 92 and 94. As more fully described in U.S. Patent No. 4,317,322, assigned to Lantech, Inc., incorporated herein by reference, these conveyors comprise driven endless belts 96 and 98 mounted on a plurality of rollers 100. The rollers are supported by plates 102 secured in turn to a frame member (not shown) which holds the rollers in a rotatable position. The upper surface of endless belt 96 is rotated in a direction shown by the arrow A and the lower surface of belt 96 frictionally engages the top surface of endless belt 98 to drive it at the same speed.
- Belt 96 is driven by a motor assembly 104 which is connected by linkage 106 in the form of chains or belts to drive the conveyors.
- the upper belt segment of conveyor 92 travels downstream with the lower segment travelling upstream.
- the upper belt segment of conveyor 94 travels upstream while the lower segment travels downstream.
- the upper and/or lower conveyor can comprise multiple belts.
- This construction allows a web of film to be wrapped around a load 24 which was carried from the infeed conveyor 32 onto the wrapping station 41.
- the stretched wrap of web is wrapped around the conveyor assembly 34 and the load with both the load and wrap being carried by the conveyor assembly in the same direction.
- the conveyor assembly and wrapping ring is stopped, the clamp apparatus 88 clamps the film web and the cutter mechanism 110 severs the film web.
- the conveyor assembly 34 is activated carrying the load and the wrap downstream to a take-off conveyor 20.
- the cutting mechanism 110 used in the preferred embodiment of the invention comprises a driven pivoted standard which is adapted to project upward to engage the film web between clamping apparatus 88 and the load 24.
- the cutting mechanism 110 comprises a support standard 112 which is pivotally mounted at 114 to a base member 116.
- the base member 116 can either be a part of frame 42 or be secured to frame 42.
- a pneumatic lifting cylinder 118 has one end mounted by a suitable ear or bracket attachment to the base member 116 with the end of its piston rod 119 attached to the support standard 112 by suitable means such as a yoke member 121. Upon activation of the pneumatic cylinder, the upright standard 112 is transported in an arcuate path into the film web 58.
- a cutting assembly 120 comprising a support plate 113, a pneumatic cylinder 122 mounted to the support plate 113, and a cutting blade assembly 123 mounted to the piston rod 126 of cylinder 122.
- a brush 128 is vertically mounted on the support plate to brush down the trailing edge of the web against the conveyor assembly.
- a bumper member 130 is positioned in front of brush 128 to protect the brush base from initial contact with the film web and conveyor assembly.
- the cutting mechanism 110 is propelled upward so that the cutting assembly 120 engages the film web.
- the blade assembly 123 subsequently severs the film web from the load.
- the cylinder 118 can be activated after cutting to propel the standard 112 forward a predetermined distance causing the brush 128 to engage the remainder of the trailing edge of the film web and wipe it against an underlying film layer.
- the conveyor assembly 34 leads from the infeed conveyor 32 to a take-off conveyor 20 which is constructed like the infeed conveyor and runs at the same speed as the infeed conveyor.
- a suitable mechanical means (not shown) is set up to make the drive of both the infeed conveyor and the take-off conveyor equal to the reduction gearing assembly of the drive motor.
- the motor slows down or speeds up to drive the wrapping mechanism at different speeds, the infeed and take-off conveyors are simultaneously. speeded up or slowed down so that the load is moved to conveyor assembly 34 and taken away from the conveyor assembly 34 at consistent relative speed.
- continuously wrapped loads are taken off of the apparatus and are severed into separate loads away from the apparatus.
- the take-off conveyor 220 carries the continuously spiral wrapped loads as shown in Figure 4 connected together by the film overrap from the wrapping station.
- the take-off conveyor assembly 220 carries the spirally wrapped bundle onto cutting conveyor 222.
- the wrapped spiral bundle 224 as seen in Figure 4 is severed into individual packages by a guillotine-like cutting apparatus 225 comprising a frame 227 and a cutter mechanism 229 slideably mounted to the frame.
- the cutter mechanism 229 consists of a bow frame 230 strung with nichrome wire 232 which is electrically connected to a source of energy. The resistance of the wire causes sufficient heat so that when the wire is reciprocated between the encapsulated loads 224 to cut them apart, the film material is simultaneously bonded to the edges so that the film will not unravel in shipment.
- a sensor 131 projects a light source through the transparent film in a space S between the individual loads against a reflector 133 to generate an electrical signal commanding the cutter blade drive circuitry to activate a pneumatic cylinder 236.
- the hot cutter wire 232 is driven through the film to sever the load 124 from the wrapped spiral bundle 224.
- any standard circuit can be used to cause the pneumatic cylinder 236 to be activated when the sensor senses a space between loads 124.
- a limit switchy contact switch, pressure sensitive switch or other suitable means can be used to activate the cylinder 236.
- the wire is heated by connection to a current source of about nine volts which heats the wire sufficiently so that the edges of the film are bonded to form a holding edge.
- the severed edge stretches back to its original memory shape to form the holding shape.
- the spiral bundle advances and the next spacing S between the loads 124 is sensed by the light sensor 131.
- Other cutting apparatus can be used in place of the heating cutting wire, namely a knife blade with sawtooth edges secured to the frame in place of the cutter wire.
- the cutting edge strikes the wrapping material substantially causing the wrapping material to shear. The cutting is done while the wrapped bundle is being transported by the conveyors.
- the predetermined load model is first configured by positioning horizontal members 172, vertical members 174 and pulleys 62 to define a polygon having an aspect ratio equal to that of a cross-section of the load.
- a ring 60 is configured with depressions positioned to decelerate downstream roller 74 as the film web approaches each edge of the load.
- feed conveyor 32 brings the load 24 onto the wrapping conveyor assembly 34 which then carries the load to a predetermined wrap position within the film dispensing path and the conveyor assembly stops, leaving the load in a stationary position.
- the leading edge 57 of the film web 58 is held in clamping assembly 88 located beneath the conveyor assembly 34 as is best seen in Figure 3. Rotation of ring 44 about the load is then begun.
- the film edge which is held by the film web wrap may be released.
- the wrap is for a full web load as shown in Figure 16 or a banded load as shown in Figure 17, a plurality of overlying layers of film are wrapped around the load and the conveyor assembly 14.
- a spiral wrap mode as shown in Figure 18, a plural number of wraps are wrapped around the downstream end of the load as shown in phantom in Figure 18 in the same manner as the banding in Figure 17 and the conveyor assembly is activated carrying the load downstream to a take-off conveyor so that a spiral wrap is formed around the load.
- both the take-off conveyor and wrapping conveyor assembly stop and a second band is placed around the upstream end of the load in the same manner as if a band or full web wrap were being wrapped around the load. It should be noted that there is a space between the conveyor assembly 34 and the take-off conveyor 20 allowing the stretched film web to be discharged from the conveyor assembly and assume its memory position M around the load.
- the end of the wrap cycle is determined in the present invention by a proximity switch 99 located a short distance away from ring 44 which senses a bent metal plate 45 secured to the ring.
- the proximity switch is electrically connected to a counter which is activated to determine each revolution of wrap.
- the particular counter which is utilized is an Eagle counter, Model D2100-AG, which is an off-the-shelf standard apparatus.
- the counter activates a switch which stops the take-off conveyor and wrapping conveyor assembly for cutting of the film web.
- the activation of the fluid cylinders to fire .in a predetermined order and extend a predetermined distance is well known in the art and can be accomplished by common fluid circuitry.
- the cutter mechanism When the cutter mechanism is activated, the cutter standard and head is directed upward and abuts the film carrying the film to the middle of the load. It should be noted that the dispensing roll 56 on ring 44 in the stop position is located underneath the load and is substantially perpendicular to the axis of the load. When the film roll has been positioned in this manner, the web itself has engaged either the load edge or conveyor assembly edge and is angled from the edge down towards the roll positioned on the ring.
- the cutter mechanism 110 when driven upward by the pneumatic cylinder 118 engages the angled film web and carries it into substantial conformance with a perpendicular line drawn from the center axis of the conveyor assembly with the brush 128 brushing the film down over an underlying film layer wrapped around the conveyor assembly as is shown in Figure 11.
- the clamping mechanism 82 is then rotated to clamp and hold the film web between the cutter head 120 and the dispensing roll 56.
- the pneumatic cylinder 122 of the cutting head is then fired, driving a sawtooth cutter blade 221 into the film web 58 to sever the film web.
- a small portion of the trailing edge is left hanging free from the wrap.
- this film edge may be wiped onto the load by firing the cutter standard cylinder 118 a second time so that the standard moves a short distance further on carrying the brush on to wipe the remnant edge against the wrap.
- the cutter standard is then withdrawn away from the load into a rest position as shown in phantom in Figure 11 for the next cutting operation and the conveyors are activated to carry the wrapped load away from the wrapping station and a new load into the wrapping station.
- the previously described cutter mechanism is not used and the loads are continuously carried along the wrapping conveyor assembly onto a take-off conveyor which spaces the loads for severing downstream. The loads are then severed between the spaced film areas as previously discussed and taken away to another transport area.
- the present inventive system provides the capability to wrap loads ⁇ with minimal variation in wrapping force and levels of elongation despite substantial variation in load demand for film.
- the user can elect to apply maximum force for high containment without risk of film failure, or to apply minimum force for delicate loads without risk of load failure or wrap loosening.
- the system continues to operate at normal speed when film web holes develop, so that web tension changes do not cause holes to enlarge. All of these characteristics contribute to the high reliability, throughput and economy of the present inventive system.
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- Engineering & Computer Science (AREA)
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Description
- The present invention generally relates to packaging and more particularly is directed to a rotating stretch wrapping apparatus for making unitary packages which hold a plurality of components, each package containing a load wrapped in a web of stretched film.
- The present invention specifically relates to an apparatus and a process for wrapping a film web around a load with a cross section which causes variations in demand rate for the film web during wrapping, said apparatus comprising a frame and dispenser means mounted on the frame for revolving around the load, and having at least one feeding roller for dispensing the film web, while said process comprising revolving a film web dispenser around the load and dispensing the film web from at least one roller in the film web dispenser to wrap the load.
- United States Patent No. 4,317,322, assigned to Lantech, Inc., disclose a pre-stretch film elongation system mounted adjacent a film roll and rotated about a stationary load. The pre-stretch system which is mounted on the rotating ring includes an upstream roller and a downstream roller across which the film web successively passes. The two rollers are coupled by gears, belts, or the like, which force a constant ratio of velocity between the rollers. Film is drawn from the film roll and across each of the rollers by relative rotation of the ring around the load. The fixed speed ratio between the upstream and downstream rollers; in which the downstream roller moves more quickly than the upstream roller, causes substantial and constant stretching between the rollers of the web. In this device the substantial changes in demand speed are transmitted directly from the load back through the web to the pre-stretch device, so that the supply speed of the film moving across the downstream roller to the load changes accordingly. However, it can be appreciated that the entire force exerted between the rollers is applied to the rollers by film being wrapped about the load, and that pre-stretch device inertia and the elasticity of the film web between the downstream roller and the load causes a phase delay or lag in supply speed changes. It has also become clear that any hole in the web, such as those which commonly occur at web imperfections or gauge variations, causes a weakening between the load and the pre-stretch mechanism, thus slowing or stopping the pre-stretch mechanism. The hole is then elongated and enlarged by the growing difference between supply and demand speeds, finally breaking the film web and interrupting the wrapping procedure.
- Furthermore, it has been discovered that two characteristics of the film wrapping systems described above combine after wrapping is completed to reduce the containment force exerted on the load. One such characteristic is that a film web segment applied to any one side of the load exhibits elongation and containment force independent of continguous film web applied to either of the sides immediately prior to or after the given side. This is because load edges isolate each film web segment applied to a side from connecting film web segments applied to adjacent sides, so that slippage across edges does not occur. Film web characteristics are thus effectively "locked in" on each side as the film web encounters the edge at the end of the side.
- The second characteristic is that, in prior art wrapping systems, locking in at load edges occurred precisely at the point where the film web experienced a minimum of force and elongation, having partly retracted and recovered from a prior maximum force/elongation point, thereby locking in the same minimum characteristics. Since a maximum force was also experienced during the wrapping of each load side, an attempt to raise overall force in order to raise the minimum point will also raise the maximum point and increase the risk of exceeding the failure point for the film web. An attempt to lower overall force for delicate loads will reduce the minimum point and risk zero containment of the load. Hence, the . prior art wrapping systems are compelled to wrap stetch- able film web to a load at containment force levels well below those levels theoretically possible, which, in turn, reduces the final post-unitizing force to the load after film web recovery and after shifting and settling has reduced the load circumference.
- The above discussed drawbacks (phased delay or lack in supply speed changes due to inertia forces) and characteristics apply as well to systems working with at least one feeding roller combined with a brake instead of the pre-stretch mechanism according to the United States Patent No. 4,317,322.
- DE-A-2,256,708 describes a wrapping apparatus wherein the supply roller is guided a path of simular configuration as the peripheral shape of the load. No means are provided for compensation of inertia forces or taking care of the above discussed characteristics.
- It is therefore an object of the invention to provide for a circular rotating wrapping apparatus and process as known from US-A-4,317,322 which incorporates at east one feeding roller, preferably a pre-stretch system and avoids the force pattern which reaches a minimum as each load edge is encountered, preferably introducing a pattern which minimize changes in force and elongation at each edge to lock in desirable web characteristics. Moreover, the apparatus and process should avoid control of the at least one feeding roller or the pre-stretch system through the film web itself, so that the feeding roller or the pre-stretch system will not decelerate when holes develop in the film web. Thus the risk of hole expansion and film failure will be minimized.
- The apparatus of the invention is therefore characterized by supply speed control means coupled to the roller through a mechanism other than the film web for increasing and decreasing the rotation speed of the roller, said supply speed control means comprising means defining a predetermined model substantially approximating the cross-sectional configuration of the load for rotatably controlling the speed of the roller in response to input from said load model, said input being independent of both actual sensed variations in the tension of the film web and actual sensed variations in the demand rate for the film web downstream of the roller, said supply control means dispensing the film web from the roller at a controlled variable supply speed according to said load model input independent of the sensed variations in the tension of the film web and sensed variations in the demand rate for the film web downstream of the roller, while the process of the invention is characterized by forming a predetermined model substantially approximating the cross-sectional configuration of the load; and controlling the rotation speed of the roller by rotatably controlling the speed of the roller through a mechanism other than the film web in response to input from said load model, said input being independent of both actual sensed variations in the tension of the film web and actual sensed variations in the demand rate for the film web downstream of the roller, and dispensing the film web from the roller at a controlled variable supply speed according to said load model input independent of sensed variations in the tension of the film web and sensed variations in the demand rate for the film web downstream of the roller.
- The present invention is directed toward an apparatus and process for applying stretchable plastic film to loads using a feed roller, preferably a pre-stretch mechanism which is driven and controlled independently of the web tension to minimize variations in the force exerted on the film web at load edges by varying the film web supply speed. Film web is drawn to the load at a demand speed which varies during rotation of a film roll about a load. The supply speed changes required to minimize web elongation and containment force changes at load edges are transmitted to the feed roller or the pre-stretch mechanism by a supply speed control mechanism using a predetermined model of the load, which permits higher levels of stretch, faster payout speeds, and use of less uniform film than were previously thought possible. The present invention reduces the likelihood of unexpected web breakage during wrapping, increases throughput and conserves film by establishing load containment with fewer web layers.
- In the apparatus a series of loads are fed into a rotating wrapping apparatus having preferably a film web pre-stretch mechanism and elongation drive mechanism. Each load is covered by a plurality of layers of stretched film to form a unitary package. The pre-stretch mechanism is mounted on a rotating ring through which a load travels for encirclement by stretched film web. The supply speed control mechanism is mounted adjacent the rotating ring. Energy is delivered to the pre-stretch mechanism during rotation of the rotating ring by way of a power pulley, cam follower or the like mounted to the pre-stretch mechanism. The power pulley engages the supply speed control mechanism and revolves at a varying rate due to friction thereon. The power pulley then transfers its energy and speed to the film pre-stretch mechanism. The pre-stretch mechanism is thus operated at a varying speed and supplied with the force required to stretch the film by the supply speed control mechanism.
- Thus, it can be seen that the invention provides a novel and useful improvement over the prior art rotating wrapping machines, both those utilizing brake stretching systems and those utilizing coupled roller stretching systems. This is advantageously accomplished without the need to transfer electrical power or control signals from a stationary source to devices such as brakes or motors on the rotating ring.
- Most plastic films when stretched above their yield point gain significantly in modulus and ultimate strength. The typical polyethylene will multiply three times the ultimate strength in pounds per square inch of cross sectional area after being elongated approximately 300 percent. This significant increase in strength begins approximately when the yield point is exceeded in the elongation phase. The term "yield point" designates a range or region on the stress-strain curve, rather than a dimensionless point. Limitations of friction-based constant force devices prevent current stretch wrap applications from achieving the higher levels of containment force and ultimate strength available in the foremost plastic films. Achieving the higher elongation levels with the invention allows wrapping with fewer revolutions of film yet maintains equivalent holding power. These higher levels of stretch not only allow fewer revolutions of film but also permit wrapping with less film by weight for each revolution.
- Thus, the present invention allows at least double the practical level of elongation currently experienced with prior art "brake" systems. This gives higher containment forces and/or lower film costs to the end user.
- Furthermore, the invention allows for more precise control of web speeds and forces thereby achieving greater cost efficiency from high yield films, along with higher film strength or modulus achieved at higher levels of elongation.
- The novel construction of the invention provides for isolation of the pre-stretch mechanism from stretch forces which eliminates premature film failure from development and elongation of holes at web imperfections. This construction eliminates friction brakes and the problems of those brakes such as speed variation, break away from stop position, temperature variation, wear and operator control meddling.
- It can thus be seen that the present invention provides a unique apparatus and process with an elongation mechanism driven to apply uniform film web containment across every side of the load. The film is preferably stretched beyond its yield point as it is accelerated. The acceleration force is provided by the supply speed control mechanism, which also precisely varies the web supply speed to lock in predetermined elongation and containment force on the load. By limiting the stretching action to a minimum distance within the elongation mechanism and avoiding secondary stretch between the elongation mechanism and the load, web neck down is significantly reduced.
- Although the invention is set forth in the claims, the invention itself and the method by which it is made and used may be better understood by referring to the following description taken in connection with the accompanying drawings forming a part hereof, in which like reference numerals refer to like parts throughout the several views and in which:
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- Figure 1 is a perspective view of the invention partly broken away disclosing a preferred embodiment of the inventive apparatus;
- Figure 2 is an enlarged reversed side elevational view of the apparatus shown in Figure 1;
- Figure 3 is an enlarged front elevational view of the apparatus shown in Figure 1;
- Figure 4 is a side elevational view of a continuous spiral bundling system with a sequence of consecutive packages wrapped by the present invention;
- Figure 5 is a graph of force versus time as exhibited by prior art wrapping apparatus;
- Figure 6 is a generalized graph of force versus elongation for film web utilized in the present invention;
- Figure 7 is a schematic representation of film web demand during relative rotation of a load;
- Figure 8 is a schematic representation of film web demand at a wrapping stage on the load subsequent to that of Figure 7;
- Figure 9 is a schematic representation of film web demand at a wrapping stage on the load subsequent to that of Figure 8;
- Figure 10 is a graph of force versus time for the preferred embodiment of the present inventive apparatus;
- Figure 11 is a front elevational view of the web cutting mechanism shown in various positions during cutting of the film web;
- Figure 12 is an enlarged front elevational view of an alternate embodiment of the present invention;
- Figure 13 is an enlarged rear elevational view of the apparatus of Figure 12;
- Figure 14 is an enlarged reversed side elevational view of the apparatus of Figure 12;
- Figure 15 is a side elevational view of the cutting apparatus of Figure 11;
- Figure 16 is a side elevational view of a full web wrap mode accomplished by the present invention;
- Figure 17 is a side elevational view of a banding wrap mode accomplished by the present invention; and
- Figure 18 is a side elevational view of a spiral wrap mode accomplished by the present invention.
- The best mode and preferred embodiment of the present invention is disclosed in Figures 1 through 3, and comprises a
ring wrapping apparatus 30 comprising afeed conveyor 32, a wrap andload conveyor assembly 34, afilm dispensing mechanism 36 with a take-offconveyor 20. - As shown in Figure 1, a plurality of
units 22 forming aload 24 have been loaded in a stacked relationship on aninfeed conveyor assembly 32 by either manual or mechanical means. It should be noted that the load, depending on its nature and composition, may or may not require spacing. Theloading device 31 is schematically shown and may be one of a number of types of stacking or placing devices which are well known in the art to place a stack of cartons or materials into designated areas. - Throughout this specification, containment force refers to force applied to a load by film web surrounding the load when wrapping is completed, while wrapping force refers to force applied by film web extending from the wrapping system to the load during wrapping. Wrapping force is, of course, applied equally and oppositely to the film web and to the load simultaneously.
- In the preferred embodiment, the
load 24 is placed on aninfeed conveyor 32 which is comprised of an endless belt 26 mounted on frame support 28. - An alternate embodiment of the infeed conveyor could take the form of a hydraulic or pneumatic pushing device (not shown) which can be used to engage each
load 24 with a platen to push the load into the wrapping area. However, the conveyor embodiment is preferred and the belts of the conveyor of the present invention are preferably textured so that they have a high coefficient of friction. - The particular arrangement of the conveyors set forth in Figures 1 and 2 lends itself to random variation of total load size in all three dimensions. It is apparent however that other configurations could be constructed which would be advantageous for specific products. Thus, the conveyance of twelve-packs or six-packs of cans or bottles could be handled by a horizontal conveyor with guide conveyors on each side.
- The conveyor belt 26 as seen in Figure 1 is mounted on rollers 29 which are rotatably journalled by suitable bearing means in brackets which are secured to the frame support 28. The
infeed conveyor 32 carries theloads 24 onto a wrappingstation 41 comprisingfilm dispensing apparatus 36, and wrappingconveyor assembly 34. - The preferred embodiment and best mode of the invention comprises a
frame 42 on which a steel "donut" or ring-shapedfilm support member 44 is rotatably mounted and supported on three planes byguide rollers 46. If desired, the film support member can be constructed of aluminum. A plurality ofguide rollers 46 project inward from theframe 42 onarms 47 and mountingplates 48 to engage the ring-shaped member so that it can be driven in a predetermined path. Afriction drive wheel 49 is positioned adjacent thering member 44 at its base and engages themember 44 to rotate themember 44 within the guide wheel rolling area. Thefriction drive wheel 49 is driven by amotor 50 having a shaft which is suitably connected with adrive reducer 52. A materialroll dispensing shaft 54 is rotatably secured to thering member 44 for rotation on its axis and is adapted to receive and hold a roll offilm material 56. - An important aspect of film wrapping apparatus performance is that the elongation and containment force exerted by any one layer of film applied across any given side of a load is not influenced by the characteristics of the same layer of film wrapped to either a prior side or a subsequent side of the load. Load edges are barriers preventing film slippage which would otherwise alter film elongation and containment force. In other words, film elongation and containment force are locked in for a given load side when the film encounters the edge at the end of the side. Thus, it is advantageous to increase the containment force and elongation just before the corner is encountered, in order to minimize wrapping force fluctuation and minimize the risk of film destruction due to excessive force at any other point in the wrap cycle.
- It has been found that the prior art supply systems lock in elongation and containment force at a minimum value when each load edge is encountered. A schematic representation of film demand rate at load edges is shown in Figures 7 through 9 in which a
pre-stretch mechanism 70 is rotated in the direction indicated by the arrow D around a center point Y at a constant angular velocity to wrap a representativerectangular load 24. In Figure 7, thefilm web 58 has just completed wrapping a long side of the load and has encountered corner X. At this point thefilm web 58 passes on a straight line frompre-stretch mechanism 70 across the long face of the load. The line offilm web 58 therefore forms a right angle with the line segment A extending from the rotation center Y to the tangent point T. At this instant, the rate of demand for film web by theload 24 during wrapping can be computed by treating the line segment A as the effective wrapping radius of a circle J to whichfilm 58 is tangent at point T. It can readily be appreciated that the rate of demand for film will increase as the effective wrapping radius increases, under constant angular rotation of thepre-stretch mechanism 70. - Turning to Figure 8, subseguent rotation of the
pre-stretch mechanism 70 has reached the point of maximum demand rate. The tangent point T is now equivalent to the corner X, and the line segment B from the corner X to the rotation center Y defines the effective wrapping radius of a circle K. It can readily be appreciated that the radius B is much longer than the radius A, so that the film demand rate in Figure 8 is much greater than the film demand rate in Figure 7. - Turning to Figure 9, further rotation of the
pre-stretch mechanism 70 about the load has completed the wrapping of the short side and encountered the corner XI subsequent to the corner X. Thefilm web 58 now lies along the short side of the load, and the line segment C from the rotation center Y to the tangent point T defines the effective wrapping radius of a circle L. It can clearly be seen that the radius C is shorter than the prior radius B, so that the linear film demand rate at this stage in wrapping the load is less than that in Figure 8. - To summarize, it can be appreciated that film web is demanded by the load at a rate which varies but is always at a minimum when a side is completely wrapped and a corner is encountered. This swing from minimum to maximum and back occurs once for each load side, or four times per revolution for a load of rectangular cross-section. If
film web 58 is dispensed frompre-stretch mechanism 70 at a constant rate, the net film web acceleration and force will follow the same pattern of variation as the demand rate. This is illustrated in Figure 5, in which acurve 190 shows the varying wrapping force experienced by the load as well as the film web between the load and the downstream roller of a typical prior art pre-stretch system. Eachminimum point 196 of thecurve 190 occurs precisely when a corner is wrapped at the completion of wrapping a side of a load. Eachmaximum point 198 ofcurve 190 occurs after theminimum point 196 occurs and before the film web characteristics are locked in for the side when a subsequent corner is encountered. Thus, it can be appreciated that the final level offorce 196 is significantly less than themaximum force level 198, during the prior art wrapping of any side of the load. - Turning now to Figure 6, a general stress-
strain curve 140 is shown which illustrates the relationship between elongation and force for a generalized film web composition. The curve region indicated at 141 is generally known as the elastic limit or yield point for the material. If, starting with no elongation; the material is stretched by a force which is sufficient to elongate the material no further than the region indicated at 141, then when the force is removed the material will return along thesame curve 140 back to zero elongation at zero force. However, if force is exerted to carry the elongation of the film web beyond the region indicated at 141, such as to the point indicated at 148, then the film web has exceeded its elastic limit and reacheselongation point 248. It will remain permanently elongated to some extent depending upon the subsequent pattern of force applied. If the subsequent force is reduced, then elongation will recover along a curve such as that shown at 150, reaching finally apoint 160 where permanent elongation is exhibited without any force whatsoever. It can be appreciated that thepoint 160 is to be avoided in film wrapping because this represents zero containment force experienced by the load. At such a point, then, the wrap sits loosely on the load and subsequent vibration or motion can cause contained units to spill out of the wrap. - The
point 148 in Figure 6 is reached at eachmaximum point 198 of the curve of Figure 5. At these points, the force experienced by the load and the web is at a level indicated atpoint 194 and film elongation is atpoint 248. When the wrap of the side is completed, however, the force is reduced to theminimum level 192, which corresponds to thepoint 162 oncurve 150 of Figure 6 and elongation level 262. Thus, in the prior art constant-speed pre-stretch systems, maximum containment force to the load is forfeited. Any reduction in load circumference after wrapping, such as is commonly experienced due to settling, allows further reduction from elongation level 262 ultimately to thepoint 160, where no containment force is exerted. This point can be reached with a relatively modest circumference reduction from point 262, typically on the order of ten percent. - In contrast, the preferred embodiment of the present invention advantageously exerts a wrapping force to a load as well as on the film web between the load and the pre-stretch mechanism which approaches
curve 300 illustrated in Figure 10, which is a flat line. Thus, there is reduced swing between minimum and maximum points in the force curve, and the force curve can easily be elevated to lock in elongation and force to the load at apoint 148 oncurve 140 of Figure 6 above theelastic limit region 141. It can be appreciated that, for a load wrapped with the present invention, extreme load circumference reduction would have to occur before containment force were relaxed to thepoint 160 illustrated in Figure 6. If the force of the prior art mechanism as illustrated in Figure 5 were merely raised so that both themaxima 198 and theminima 196 were higher, there is a substantial risk that themaxima 198 will exceed the force point at which film destruction occurs. However, the performance of the present invention elevates and flattens the load force curve so that the force to the load closely approaches the film destruction point without any risk of exceeding it. - The force curve can also be easily depressed to wrap delicate loads at low wrapping force without risk of a variation eliminating containment force completely.
- Typical films which can be used in the stretch wrapping apparatus are EVA copolymer films with a high EVA content such as the films manufactured by Consolidated Thermoplastics "RS-50", Bemis "Super-Tough", and PPD "Stay-Tight" films. PVC films such as Borden Resinite "PS-26" can be used in the invention along with premium films such as Mobil-X, Presto premium and St. Regis which utilize a low pressure polymerization process resin manufactured by Union Carbide and Dow Chemical Company. This resin, called linear low density polyethylene, has significantly different stretch characteristics than previous stretch films. These characteristics allow the film to withstand the high stress of extreme elongation without tearing during wrapping of the load.
- It should be noted that film, film material and film web are used interchangeably throughout the specification.
- Turning to Figures 1 through 3, supply
speed control mechanism 90 comprises apulley frame 39 parallel to ringmember 44 fixed to frame 42, and a plurality of double-sheave pulleys 62 rotably mounted onshafts 63 journalled to frame 39. Theframe 39 compriseshorizontal members 172 defining lengthwiseslots 173, andvertical members 174 defining lengthwiseslots 175.Bolts 176 are placed throughslots members Shafts 63 may be threaded at a frame end and locked with threaded nuts into a particular spacing inslots 174. Theshafts 63 are placed so that they define corners of a polygon having an aspect ratio equal to that of a load cross-section. The term "aspect ratio equal" here means identical length ratios of adjacent sides and identical edge angles therebetween. Two polygons having equal side ratios and equal edge angles are said to have identical aspect ratios even though one may enclose greater area than another. It will be appreciated that the illustrated form offrame 39 permits easy adjustment to accomodate variation in load cross-section. Although fourpulleys 62 and arectangular frame 39 are shown in the drawings, this number is exemplary only and any appropriate number of pulleys and sides may be utilized. Apower belt 64 passes around anouter sheave 65 of eachpulley 62, and adrive belt 66 passes around aninner sheave 67 of eachpulley 62.Belts - A
power pulley 68 mounted onpower axle 61 acrossring member 44 engagesbelt 64 so that rotation ofring member 44 relative to belt 64 causespulley 68 andaxle 61 to rotate in an opposite direction at a speed which varies in each revolution ofring member 44 due to passage ofbelt 64 around pulleys 62.Drive belt 66 also engages drivepulley 78 mounted to a rotating output shaft ofdrive motor 81, so thatbelt 64 is driven bymotor 81 and the speed ofmotor 81 may be adjusted to increase or decrease the rate of relative rotation betweenbelt 64 andring member 44 without affecting the rotation rate ofring member 44 relative to the load. - The film web is drawn from
roll 56 through a pre-stretching orelongation mechanism 70 and is tucked or fastened underneath or held adjacent the load. The pre-stretching mechanism ,70 which is best seen in Figure 2, comprises connectedroller members shafts housing 76. Thehousing 76 is mounted to and across the plane of thering member 44.Gears 77 and 79 are mounted respectively toshafts speed control mechanism 90 as the film web engages the rubber roller surfaces. The film web passes first across theupstream roller 72 and then across thedownstream roller 74 as it is pulled fromfilm roll 56 to theload 24, and thegears 77 and 79 operate as an elongation control to rotatedownstream roller 74 faster than theupstream roller 72, causing the film to be accelerated and stretched in anarrow space 80 between the two rollers. The ratio of thegear 77 to the gear 79 preferably ranges from 3:2 to 4:1, so thatdownstream roller 74 rotates faster thanupstream roller 72 by a ratio ranging from 3:2 to 4:1. While a two-roller elongation system is preferred, it is an obvious modification to utilize any number of rollers therein, including a single roller pulling against a restrained film roll. -
Film roll 56 can be urged againstupstream roller 72 in any well-known conventional manner such as by a coil spring (not shown), which maintains friction ofupstream roller 72 and film roll 56 as film payout reduces the diameter offilm roll 56. Contact ofroller 72 and roll 56 prevents uncontrolled payout of film web due to momentum offilm roll 56 upon deceleration ofroller 72 during normal operation. - Alternatively a pivoting
collar 83 may be placed aroundupstream roller shaft 73, and a countereight 85 andcontact frame 84 may be mounted at angles to thecollar 83. At an end offrame 84 opposite thecollar 83, acontact roller shaft 51 is rotatably journalled to frame 84. Contactroller 57 is mounted to an end ofshaft 51adjacent roll 56 for engagement withroll 56. Contactroller pulley 53 is mounted to an end ofshaft 51opposite roller 57. Anupstream pulley 55 is mounted toshaft 73.Pulleys pulley belt 59, and the ratio of pulley sizes and the circumference ofroller 57 are chosen such that the linear surface speed ofroller 57 is slightly less than the linear speed ofupstream roller 72. Acoil spring 86 is coupled to frame 84 andhousing 76 so as to constantly urgecontact roller 57 against the surface offilm roll 56 which decreases in radius asfilm web 58 is paid out during wrapping.Spring 86forces roller 57 to maintain contact with the surface ofroller 56 during rotation ofring member 44.Counterweight 85 exerts leverage onframe 84 to compensate for the effect of the force of gravity onroller 57 asring member 44 rotates. Therefore, friction betweenroller 57 andfilm roll 56 will be maintained, and pay out speed offilm web 58 fromroll 56 will accelerate and decelerate precisely to match speed changes of the elongation system. -
Shaft 61 extends through housing 76 a distance at least equal to the distance betweenrotary ring 44 andpulleys 62 for interaction with supply speed control means 90. Apower pulley 68 is mounted on the end ofshaft 61 so as to engagebelt 64 asring member 44 rotates. Contact ofpulley 68 andbelt 64 is maintained throughout the revolution ofring member 44, and tension onbelt 64 is mintained by pressure oftensioner roller 69, which is spring-loaded in any well known conventional manner.Belts pulleys - An end of
shaft 61 opposite that to whichpulley 68 is mounted extends beyond thehousing 76, and transferpulley 21 is mounted thereto. An end ofdownstream roller shaft 75 likewise extends beyond the side ofhousing 76 wherepulley 21 is mounted, anddownstream roller pulley 25 is mounted to it.Transfer belt 23 engagespulleys downstream roller 74 is driven to rotate at a speed proportional to that ofpulley 68 viashaft 61,pulley 21,belt 23 andpulley 25. - Reduced variation in force to the load is achieved because the film supply rate from the
pre-stretch mechanism 70 varies precisely as the film demand rate to the load varies, so that the net acceleration difference between the rates is constant. The film supply rate is controlled by the rate of passage ofbelt 64 acrosspulley 68, which varies asbelt 64 encounters each pulley corresponding to a load corner. Because theload 24 and thepulleys 62 share a common aspect ratio, the speed ofbelt 64 varies precisely as shown in Figure 5 for the same reasons, illustrated in figures 7 through 9, that the film demand rate varies along the curve shown in Figure 5. That is, the portion ofbelt 64 trailing frompulley 68 is demanded or pulled away bypulleys 62 at a rate which varies according to the changing effective wrapping radius around pulleys 62, just as the film is pulled away frompre-stretch mechanism 70 to theload 24 at a rate which varies according to the changing effective wrapping radius around the load. As illustrated, the film supply rate changes from a minimum to a maximum and back four times per dispenser revolution about a load of rectangular cross-section, but other configurations ofpulleys 62 can be used with equal effectiveness for loads of other cross-sectional shapes. Thus thepulleys 62 andbelt 64 of supply speed control means 90 serve as a predetermined model of theload 24 which controls the output rate ofpre-stretch mechanism 70 without reliance on feedback through film web betweenroller 74 and the load. So long as the angles and ratios of side lengths remain equal for thepulley 62 area and the load cross-section, the demand rate forbelt 64 will follow the load demand rate forfilm 58. - An alternate embodiment of the supply speed control mechanism designated 95 is illustrated in figures 12 through 14. The
belt 65,motor 81,pulley 78,pulley 68,pulley 63,frame 39, pulleys 62, and tension idler 69 are omitted. In this embodiment ring ortrack 60 is configured as a solid surface having a series of consecutive areas of greater or lesser radius, which may be considered as cam bumps or depressions respectively. The number and spacing ofdepressions 97 corresponds to the number and spacings of load vertices for purposes which will become apparent below. - In the alternate embodiment a
power column 182 is mounted to power axle collar 181. Thecolumn 182 extends beyond thehousing 76, and asecond collar 183 is mounted at an end ofcolumn 182 remote from collar 181. Anaxle 184 passes throughcollar 183 and extends to the plane ofring 60. At the end ofaxle 184adjacent ring 60, acontact roller 185 is mounted toaxle 184. A tensionedcoil spring 189 extends fromhousing 76 tocollar 183 in order to urgeroller 185 against the surface ofring 60 during rotation ofring 44. At an end ofaxle 184 opposite thecontact roller 185,pulley 186 is mounted to theaxle 184. Asecond pulley 187 is mounted topower axle 61, and abelt 188 engagespulleys - As
ring 44 rotates at a constant speed,contact roller 185 is driven to rotate by friction againstring 60. The rotation ofcontact roller 185 in turn rotatesaxle 184,pulley 186,belt 188,pulley 187 andpower axle 61.Power axle 61 acts to drive elongation amd dispensation offilm web 58 as described above for the preferred embodiment. However, the rate of rotation ofcontact roller 185 increases across each raised portion ofring 60 and decreases in each depression ofring 60, with thecolumn 182 acting as a cam follower by pivoting aboutpower axle 61 to maintain contact betweenring 60 andcontact roller 185. - Each
depression 97 ofring 60 is positioned so as to reducecontact roller 185 speed and thereby minimize the supply speed V, of film web across thedownstream roller 74 precisely when acorresponding edge 89 of the load is approached by thefilm web 58. The depth of eachdepression 97 is sufficient to maintain the difference between the takeup speed V2 and the supply speed V, to minimize the force and elongation variations as each load edge is encountered byfilm web 58. Following the edge, theroller 185 encounters a plateau onring 60, with a corresponding greater linear circumferential distance per unit of angular rotation ofring 44. The linear speed ofroller 185 will increase, correspondingly increasing the supply speed V, offilm web 58 leaving thedownstream roller 74. Thus the alternate embodiment achieves the desired effect of uniform acceleration, elongation and force at each load edge to lock in containment on each side of the load. As illustrated, the alternate embodiment decelerates and accelerates the speed V, offilm web 58 four times per revolution of the system about a load of rectangular crosssection, but other patterns ofdepressions 97 could be used with equal effectiveness for loads of other cross-sections. Thus thering 60 comprises a predetermined model of the load which controls the output rate ofpre-stretch mechanism 70 without reliance on feedback through film web betweenroller 74 and the load. - The wrapping
conveyor assembly 34 as best seen in Figure 14 comprises twostacked conveyors endless belts rollers 100. The rollers are supported byplates 102 secured in turn to a frame member (not shown) which holds the rollers in a rotatable position. The upper surface ofendless belt 96 is rotated in a direction shown by the arrow A and the lower surface ofbelt 96 frictionally engages the top surface ofendless belt 98 to drive it at the same speed.Belt 96 is driven by amotor assembly 104 which is connected bylinkage 106 in the form of chains or belts to drive the conveyors. The upper belt segment ofconveyor 92 travels downstream with the lower segment travelling upstream. The upper belt segment ofconveyor 94 travels upstream while the lower segment travels downstream. The upper and/or lower conveyor can comprise multiple belts. - This construction allows a web of film to be wrapped around a
load 24 which was carried from theinfeed conveyor 32 onto the wrappingstation 41. The stretched wrap of web is wrapped around theconveyor assembly 34 and the load with both the load and wrap being carried by the conveyor assembly in the same direction. In the full web, spiral and banding modes, the conveyor assembly and wrapping ring is stopped, the clamp apparatus 88 clamps the film web and thecutter mechanism 110 severs the film web. Theconveyor assembly 34 is activated carrying the load and the wrap downstream to a take-offconveyor 20. When the load encounters the take-offconveyor 20 as shown in Figure 14, the elongated stretched web coming off of the end of the conveyor assembly assumes its memory position M against the load in the space between theconveyor assembly 34 and take-offconveyor 20, allowing the contained load covered by stretched wrap to be carried away. - As shown in Figures 1.1 and 15, the
cutting mechanism 110 used in the preferred embodiment of the invention comprises a driven pivoted standard which is adapted to project upward to engage the film web between clamping apparatus 88 and theload 24. Thecutting mechanism 110 comprises a support standard 112 which is pivotally mounted at 114 to abase member 116. Thebase member 116 can either be a part offrame 42 or be secured to frame 42. Apneumatic lifting cylinder 118 has one end mounted by a suitable ear or bracket attachment to thebase member 116 with the end of itspiston rod 119 attached to thesupport standard 112 by suitable means such as ayoke member 121. Upon activation of the pneumatic cylinder, theupright standard 112 is transported in an arcuate path into thefilm web 58. Mounted to the support standard is a cuttingassembly 120 comprising asupport plate 113, apneumatic cylinder 122 mounted to thesupport plate 113, and acutting blade assembly 123 mounted to thepiston rod 126 ofcylinder 122. Abrush 128 is vertically mounted on the support plate to brush down the trailing edge of the web against the conveyor assembly. Abumper member 130 is positioned in front ofbrush 128 to protect the brush base from initial contact with the film web and conveyor assembly. Upon appropriate activation, as for example a predetermined number of revolutions of the ring member, which is sensed by an appropriate sensor device, thecutting mechanism 110 is propelled upward so that the cuttingassembly 120 engages the film web. Theblade assembly 123 subsequently severs the film web from the load. If desired, thecylinder 118 can be activated after cutting to propel the standard 112 forward a predetermined distance causing thebrush 128 to engage the remainder of the trailing edge of the film web and wipe it against an underlying film layer. - The
conveyor assembly 34 leads from theinfeed conveyor 32 to a take-offconveyor 20 which is constructed like the infeed conveyor and runs at the same speed as the infeed conveyor. In order to control both conveyors at the same rate of speed, a suitable mechanical means (not shown) is set up to make the drive of both the infeed conveyor and the take-off conveyor equal to the reduction gearing assembly of the drive motor. Thus, if the motor slows down or speeds up to drive the wrapping mechanism at different speeds, the infeed and take-off conveyors are simultaneously. speeded up or slowed down so that the load is moved toconveyor assembly 34 and taken away from theconveyor assembly 34 at consistent relative speed. - In an alternate mode of wrapping, continuously wrapped loads are taken off of the apparatus and are severed into separate loads away from the apparatus. In this embodiment, the take-off
conveyor 220 carries the continuously spiral wrapped loads as shown in Figure 4 connected together by the film overrap from the wrapping station. The take-offconveyor assembly 220 carries the spirally wrapped bundle onto cutting conveyor 222. - The wrapped
spiral bundle 224 as seen in Figure 4 is severed into individual packages by a guillotine-like cutting apparatus 225 comprising aframe 227 and acutter mechanism 229 slideably mounted to the frame. Thecutter mechanism 229 consists of abow frame 230 strung withnichrome wire 232 which is electrically connected to a source of energy. The resistance of the wire causes sufficient heat so that when the wire is reciprocated between the encapsulatedloads 224 to cut them apart, the film material is simultaneously bonded to the edges so that the film will not unravel in shipment. As the con-tinuouslywrapped bundle 224 enters the cutting area, asensor 131 projects a light source through the transparent film in a space S between the individual loads against areflector 133 to generate an electrical signal commanding the cutter blade drive circuitry to activate apneumatic cylinder 236. Upon activation, thehot cutter wire 232 is driven through the film to sever theload 124 from the wrappedspiral bundle 224. Such sensing apparatus are well known in the art, and any standard circuit can be used to cause thepneumatic cylinder 236 to be activated when the sensor senses a space between loads 124. Likewise, a limit switchy contact switch, pressure sensitive switch or other suitable means can be used to activate thecylinder 236. - The wire is heated by connection to a current source of about nine volts which heats the wire sufficiently so that the edges of the film are bonded to form a holding edge. The severed edge stretches back to its original memory shape to form the holding shape. The spiral bundle advances and the next spacing S between the
loads 124 is sensed by thelight sensor 131. - Other cutting apparatus can be used in place of the heating cutting wire, namely a knife blade with sawtooth edges secured to the frame in place of the cutter wire. When the blade is driven against the film, the cutting edge strikes the wrapping material substantially causing the wrapping material to shear. The cutting is done while the wrapped bundle is being transported by the conveyors.
- In the operation of the preferred embodiment of the inventive wrapping apparatus, the predetermined load model is first configured by positioning
horizontal members 172,vertical members 174 andpulleys 62 to define a polygon having an aspect ratio equal to that of a cross-section of the load. In the alternative embodiment, aring 60 is configured with depressions positioned to deceleratedownstream roller 74 as the film web approaches each edge of the load. The full web, spiral web, and banding modes of operation are operated in a substantially identical manner. In these modes, feedconveyor 32 brings theload 24 onto the wrappingconveyor assembly 34 which then carries the load to a predetermined wrap position within the film dispensing path and the conveyor assembly stops, leaving the load in a stationary position. The leadingedge 57 of thefilm web 58 is held in clamping assembly 88 located beneath theconveyor assembly 34 as is best seen in Figure 3. Rotation ofring 44 about the load is then begun. - As
ring 44 rotates, the contact ofbelt 64 withpulley 68 forces pulleys 68 and 21 to rotate at a speed which varies asbelt 64 changes position with respect to pulleys 62.Pulley 55 rotatesbelt 59 which in turn drivespulley 57 anddownstream roller 74 onshaft 75. Film is drawn fromfilm roll 56 across the surface ofroller 74 to encircle the load. Thus, the rotation speed ofroller 74 is independent of changes in the linear speed of the film web being wrapped on the load. Throughgears 79 and 77, the rotation speed ofupstream roller 72 is held to a constant ratio of that ofdownstream roller 74, so that whenupstream roller 72contacts film roll 56 and engages the film web, the film web is stretched during passage between the rollers due to the speed differential therebetween. Thus, the wrapping force changes experienced by the load in its effort to draw film acrossupstream roller 72 anddownstream roller 74 are reduced, and the variations in speed of the film web due to edge passage on the load do not change wrapping force on the film. - After at least one wrap has been made around the load and the clamp assembly, the film edge which is held by the film web wrap may be released. If the wrap is for a full web load as shown in Figure 16 or a banded load as shown in Figure 17, a plurality of overlying layers of film are wrapped around the load and the conveyor assembly 14. In the spiral wrap mode as shown in Figure 18, a plural number of wraps are wrapped around the downstream end of the load as shown in phantom in Figure 18 in the same manner as the banding in Figure 17 and the conveyor assembly is activated carrying the load downstream to a take-off conveyor so that a spiral wrap is formed around the load. When the load reaches a station where the end is sensed by a feeler gauge, light sensing means, pressure sensitive switch or other suitable sensing mechanism, both the take-off conveyor and wrapping conveyor assembly stop and a second band is placed around the upstream end of the load in the same manner as if a band or full web wrap were being wrapped around the load. It should be noted that there is a space between the
conveyor assembly 34 and the take-offconveyor 20 allowing the stretched film web to be discharged from the conveyor assembly and assume its memory position M around the load. - The end of the wrap cycle is determined in the present invention by a
proximity switch 99 located a short distance away fromring 44 which senses abent metal plate 45 secured to the ring. The proximity switch is electrically connected to a counter which is activated to determine each revolution of wrap. The particular counter which is utilized is an Eagle counter, Model D2100-AG, which is an off-the-shelf standard apparatus. When the counter has indicated a predetermined number of revolutions determined by the type of wrap and the load desired to be wrapped, the counter activates a switch which stops the take-off conveyor and wrapping conveyor assembly for cutting of the film web. The activation of the fluid cylinders to fire .in a predetermined order and extend a predetermined distance is well known in the art and can be accomplished by common fluid circuitry. When the cutter mechanism is activated, the cutter standard and head is directed upward and abuts the film carrying the film to the middle of the load. It should be noted that the dispensingroll 56 onring 44 in the stop position is located underneath the load and is substantially perpendicular to the axis of the load. When the film roll has been positioned in this manner, the web itself has engaged either the load edge or conveyor assembly edge and is angled from the edge down towards the roll positioned on the ring. Thecutter mechanism 110 when driven upward by thepneumatic cylinder 118 engages the angled film web and carries it into substantial conformance with a perpendicular line drawn from the center axis of the conveyor assembly with thebrush 128 brushing the film down over an underlying film layer wrapped around the conveyor assembly as is shown in Figure 11. The clamping mechanism 82 is then rotated to clamp and hold the film web between thecutter head 120 and the dispensingroll 56. Thepneumatic cylinder 122 of the cutting head is then fired, driving asawtooth cutter blade 221 into thefilm web 58 to sever the film web. When the film web is severed, a small portion of the trailing edge is left hanging free from the wrap. If desired, this film edge may be wiped onto the load by firing the cutter standard cylinder 118 a second time so that the standard moves a short distance further on carrying the brush on to wipe the remnant edge against the wrap. The cutter standard is then withdrawn away from the load into a rest position as shown in phantom in Figure 11 for the next cutting operation and the conveyors are activated to carry the wrapped load away from the wrapping station and a new load into the wrapping station. - In the continuous wrapping operation, the previously described cutter mechanism is not used and the loads are continuously carried along the wrapping conveyor assembly onto a take-off conveyor which spaces the loads for severing downstream. The loads are then severed between the spaced film areas as previously discussed and taken away to another transport area.
- It can readily be appreciated that the present inventive system provides the capability to wrap loads` with minimal variation in wrapping force and levels of elongation despite substantial variation in load demand for film. As a result, the user can elect to apply maximum force for high containment without risk of film failure, or to apply minimum force for delicate loads without risk of load failure or wrap loosening. Also, the system continues to operate at normal speed when film web holes develop, so that web tension changes do not cause holes to enlarge. All of these characteristics contribute to the high reliability, throughput and economy of the present inventive system.
Claims (34)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US58279784A | 1984-02-23 | 1984-02-23 | |
US582797 | 1984-02-23 |
Publications (3)
Publication Number | Publication Date |
---|---|
EP0152960A2 EP0152960A2 (en) | 1985-08-28 |
EP0152960A3 EP0152960A3 (en) | 1986-10-22 |
EP0152960B1 true EP0152960B1 (en) | 1989-06-28 |
Family
ID=24330550
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP85101960A Expired EP0152960B1 (en) | 1984-02-23 | 1985-02-22 | Rotatable film wrapping apparatus and process for unitizing a load with a compressive overwrap |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0152960B1 (en) |
CA (1) | CA1241588A (en) |
DE (1) | DE3571229D1 (en) |
GB (1) | GB2154536A (en) |
Families Citing this family (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3604509A1 (en) * | 1986-02-13 | 1987-08-20 | Dvt Verpackungstechnik Gmbh & | BANDAGING MACHINE |
DE3941940C1 (en) * | 1989-12-19 | 1991-03-21 | B. Hagemann Gmbh & Co, 4430 Steinfurt, De | |
DK166891A (en) * | 1991-09-30 | 1993-03-31 | Ebbe Korsgaard | PROCEDURE AND APPARATUS FOR MAKING A WRAPLE WRAPPED STRESS OF PRESSED BALLS OF VEGETABLE MATERIAL |
AU676117B1 (en) * | 1995-09-22 | 1997-02-27 | Itw Limited | Film stretching mechanism |
IT1308997B1 (en) * | 1999-02-16 | 2002-01-15 | Robopac Sistemi Srl | MACHINE FOR THE WRAPPING OF GROUPS OF PRODUCTS WITH PLASTIC FILM. |
ITBO20050780A1 (en) * | 2005-12-22 | 2007-06-23 | Atlanta Stretch S P A | RING MACHINE, WITH VERTICAL OR HORIZONTAL AXIS, FOR THE WRAPPING WITH EXTENSIBLE FILM AND MIXED BY USUAL PACKED LOADS. |
ITMO20060221A1 (en) | 2006-07-07 | 2008-01-08 | Aetna Group Spa | WRAPPING MACHINE AND WINDING METHODS |
ITBO20070281A1 (en) * | 2007-04-18 | 2008-10-19 | Atlanta Stretch S P A | APPARATUS TO ALLOW THE MACHINES WHICH WIND THE USED OF LOADS WITH USED AND PALLETIZED LOADS WITH AN EXTENSIBLE FILM, AND TO OPERATE ALSO AT HIGH SPEED AND WITH A SUITABLE AND PERMANENT CONTROL OF THE VOLTAGE OF THE FILM ON THE LOADED LOAD. |
GB2552214A (en) * | 2016-07-14 | 2018-01-17 | Kuhn-Geldrop Bv | Bale wrapper and method of applying stretch film wrapping to an agricultural bale |
CN106697366B (en) * | 2016-12-21 | 2023-03-14 | 福德机器人(成都)有限责任公司 | Glass fiber yarn group coating machine |
CN111252309A (en) * | 2020-04-14 | 2020-06-09 | 安阳工学院 | Film pre-winding cutting device and method thereof |
CN114194442B (en) * | 2021-09-24 | 2023-06-13 | 浙江恒成硬质合金有限公司 | Packing device for comprehensively winding heavy objects |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4317322A (en) * | 1980-05-20 | 1982-03-02 | Lantech, Inc. | Rotatable film wrapping apparatus with wrap carrying mechanism |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2256708A1 (en) * | 1972-11-18 | 1974-05-22 | Transporttechnik Gmbh | WRAPPING MACHINE |
US4050220A (en) * | 1975-04-15 | 1977-09-27 | Lancaster William G | Spiral bundler |
DE2750780A1 (en) * | 1977-11-14 | 1979-05-17 | Franpack Gmbh Verpackungsmasch | Palletised load stretch wrapping machine - has compensation mechanism for sheet irregularities caused by rectangular pallet |
CA1169349A (en) * | 1979-09-12 | 1984-06-19 | Lantech Inc. | Stretch wrapping apparatus and process |
US4302920A (en) * | 1979-11-21 | 1981-12-01 | Lantech Inc. | Film web drive stretch wrapping apparatus and process |
US4458467A (en) * | 1981-03-31 | 1984-07-10 | Infra Pak (Dallas), Inc. | Pretensioner for stretchable film web with dancer roller compensation |
FR2528020A1 (en) * | 1982-06-07 | 1983-12-09 | Procter & Gamble Europ | METHOD AND DEVICE FOR REGULATING PRE-STRETCHING OF A FILM OF PLASTIC MATERIAL, ESPECIALLY FOR THE PACKAGING OF A LOAD |
US4524568A (en) * | 1982-08-27 | 1985-06-25 | Lantech, Inc. | Power assisted rotatable film wrapping apparatus |
-
1985
- 1985-02-22 GB GB08504584A patent/GB2154536A/en not_active Withdrawn
- 1985-02-22 CA CA000474977A patent/CA1241588A/en not_active Expired
- 1985-02-22 EP EP85101960A patent/EP0152960B1/en not_active Expired
- 1985-02-22 DE DE8585101960T patent/DE3571229D1/en not_active Expired
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4317322A (en) * | 1980-05-20 | 1982-03-02 | Lantech, Inc. | Rotatable film wrapping apparatus with wrap carrying mechanism |
Also Published As
Publication number | Publication date |
---|---|
GB8504584D0 (en) | 1985-03-27 |
GB2154536A (en) | 1985-09-11 |
EP0152960A3 (en) | 1986-10-22 |
CA1241588A (en) | 1988-09-06 |
DE3571229D1 (en) | 1989-08-03 |
EP0152960A2 (en) | 1985-08-28 |
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