Technical Field

The invention relates to equipment for testing pressure tightness of plastic packaging, and, more specifically, to a system, integrable into production equipment, for testing pressure tightness of newly manufactured plastic containers for liquids and method of testing using such equipment.

Background

Packaging for liquids, such as bottles based on PET, PP, and other similar materials can be manufactured with defects that can impair tightness of a package. Leakage-causing defects can occur because of defective preforms, damage to preforms during transportation, manipulation, and packaging, bottle formation.

Bottles with liquids are usually transported by stacking them five or more levels on top of each other, depending on the design of the bottles, their volumes, and the vertical pressure they can withstand. When some damaged package leaks liquid, the liquid flows out onto the packages below. Labels can be damaged, or cardboard inserts between the bottles can collapse. Also, the entire palette may lose stability, falling and damaging other packages, products, etc., therefore, preliminary package inspection is important to avoid losses.

During pressure tightness testing, it is possible to determine whether each manufactured bottle will be able to withstand pressure or if does not have holes.

By using pressure tightness testing tools, it is possible to detect packaging defects that may not be visible by visual inspection.

Typically, the testing equipment is included into the production line as a separate unit after the bottles have been formed. The most common solution is to test finished bottles on a conveyor by sealing at the top of the bottle neck and pressurizing the package. Thus, the following defects can be identified:

- Distorted neck geometry, cracks, plastic curling;

- Determining holes in geometry of a bottle, regardless of where it is located in a package, observing pressure created in the package and the resulting drop in the event of defect through which air escapes; - When testing for tightness is performed on a conveyor, pressure resistance and pressure change of the package can be tested by pressing from the top.

Common solutions found on the market include pressure testing equipment separate from production equipment. The pressure testing equipment is placed between the package manufacturing equipment and the downstream line. They are of various sizes, depending on the testing speed, so to check the quality of the manufactured package, it is necessary to evaluate possibilities of size of existing production premises.

German patent application no. 19721529.7 (document number - DE19721529A1) describes a system for transferring bottles made from preforms from a mould through a holder while testing a product's internal cavity for tightness. A manipulator located above the holder has a testing/gripping head. To seal off the bottle in preparation for the test, the head is inserted in the bottle neck and, whilst the bottle is still in the auxiliary mould, the leak test is performed. The testing/gripping head can lift the bottle and carry it along a track. Tightness testing of the bottles is performed in the holder and/or while transporting the bottles along the path. The gripper comprises an expandable portion that expands when the element is pulled, and the element seals the neck of the bottle. The main disadvantages of the system are that bottles are tested and transported by the single unit, and the lack of cooling of the bottles before they are grabbed for transporting and testing. Also, when transport/checking assembly operates by this principle with high performance, due to the forces arising during the movement (air resistance, which acts on the bottle on the entire side surface, moment of force arising at beginning of the movement due to the fixation of the bottle at the neck and the farthest point at the bottom of the bottle, as well as pressure force in absence of a support) a leak at the neck is possible, which can lead to incorrect measurement data, or the supplied air can blow the bottle off the gripper. When testing packages shortly after they are formed, or in the same equipment, pressure testing equipment can damage the package before it has fully cooled. When testing uncooled packaging in any case, by vacuuming or by applying pressure, the geometry of the packaging may change, and the bottom may be irreversibly deformed due to the pressure. The invention does not have the above disadvantages and comprise additional advantages. Brief Description of the Invention

The disclosed pressure testing system for testing tightness of packaging is designed to be integrated into packaging manufacturing equipment. A manufactured package is inspected inside the package production equipment before being removed from it for transfer to a conveyor line or a packing equipment. The package tightness pressure testing system comprise a first mounting frame for mounting the testing system components to the packaging manufacturing equipment frame. On the first mounting frame of the system, air distributors, pressure relays, and a manipulator are mounted. The pressure testing system also comprise an air receiver and a precision pressure regulator, which are freely attached to the frame of the packaging equipment. The pressure testing system also comprise a unit for cooling bottoms of packages. The cooling unit acts as a support for the packages and a frame for its attachment to the frame of the package production unit.

Brief Description of the Drawings Features of the invention believed to be novel and inventive are set forth with particularity in the appended claims. The invention itself, however, may be best understood by reference to the following detailed description of the invention, which describes exemplary embodiments, given in non-restrictive examples, of the invention, taken in conjunction with the accompanying drawings, in which: Fig. 1 shows the testing system mounted on a frame of a packaging production equipment. Fig. 2 shows the testing system, front view, where the bottom-of-package cooling unit is not shown.

Fig. 3 shows the testing system, rear view, where the bottom-of-package cooling unit is not shown. Fig. 4 shows the testing system’s manipulator head with two grippers.

Fig. 5 shows the testing system’s manipulator head with four grippers.

Fig. 6 shows the testing system’s gripper placed on a neck of a package.

Fig. 7 shows the package cooling unit of the test system, from one side.

Fig. 8 shows the package cooling unit of the test system, from the other side. Preferred embodiments of the invention will be described herein below with reference to the drawings. Each figure contains the same numbering for the same or equivalent element. Detailed description of embodiments of the invention

It should be understood that numerous specific details are presented in order to provide a complete and comprehensible description of the invention embodiment. However, the person skilled in technical field will understand that the embodiment examples do not limit the application of the invention which can be implemented without these specific instructions. Well-known methods, procedures and components have not been described in detail for the embodiment to avoid misleading. Furthermore, this description should not be considered to be constraining the invention to given embodiment examples but only as one of possible implementations of the invention.

Although exemplary embodiments of the invention, or aspects thereof, as illustrated and described, include many components that are depicted in a particular common space or location, some components may also be remote. It should also be understood that the examples given are not limited to the components described but also include other elements required for their functioning and interaction with other components, the existence of which is self-explanatory and therefore not detailed.

The package tightness pressure testing system comprises a first mounting frame (1) of the system for mounting the system’s components (2, 3, 7) to a package production equipment frame (R). The air distributors (2), the pressure relays (3) and the manipulator (7) are attached to the first frame (1). The pressure testing system also comprise an air receiver (6) and a precision pressure regulator (9), which are freely attached to the package production equipment frame (R) through a frame (K) for mounting the receiver (6). The pressure testing system also comprises a package-bottom-cooling unit (10) and frames (31 , 34) for attaching the package-bottom-cooling unit (10) to the package production equipment frame (R).

The first mounting frame (1 ) of the system comprise a substantially horizontal crossbar (HS) and two substantially vertical crossbars (VS', VS"). The horizontal crossbar (HS) is fixed between the mentioned two vertical crossbars (VS', VS"). The vertical crossbars (VS', VS"), at their ends, each comprise an additional crossbar (TM', TM", TM'", TM'"’) which is connected to the corresponding vertical crossbar (VS', VS") so that it is directed to the production equipment frame (R) and perpendicular to the vertical crossbar (VS', VS"). Each additional crossbar (TM', TM", TM"', TM"") comprise at least one fastening element (TE), such as a bolt. Said fastening element (TE) should be of such a length that it extends through the entire thickness of packaging production equipment frame element (R), to which the first mounting frame (1) of the system is attached, and behind it, i.e., the free end of the bolt, which protrudes beyond packaging production equipment frame element (R) could be screwed in with a nut or locked with another locking element.

The testing system manipulator (7) is fixed to the horizontal crossbar (HS) through the fastening bracket (L) at the manipulator’s first end (G1). The manipulator (7) of the testing system is brought forward at a distance from the horizontal crossbar (HS) and perpendicular to the fastening bracket (L), which is connected perpendicularly to the horizontal crossbar (HS) so that the testing system’s manipulator (7) is positioned at greater distance from the packaging production equipment frame (R) than the horizontal crossbar (HS). Thus, a space is left in the first testing system’s mounting frame (1) for mounting other system elements, such as air distributors (2), and pressure relays (3). The horizontal crossbar (HS) allows positioning of the testing system’s manipulator (7) by attaching the testing system’s manipulator to it so that the testing system’s manipulator (7) is fixed next to a package take out unit (IL) together with the package (PK) removal grippers (IM', IM"). The package (PK) take-out unit (IL) with package removal grippers (IM', IM") protrudes from the packaging production equipment frame (R), under the horizontal crossbar (HS) and next to the testing system's manipulator (7), to the side between the testing system's manipulator (7) and the vertical crossbar (VS").

The test system's manipulator (7) extends vertically downwards from it’s fastening point to the horizontal crossbar's (HS) fastening bracket (L). On the other end (G2) of the testing system's manipulator (7), where the other end (G2) is on the opposite side of the testing system's manipulator (7), as viewed along the testing system's manipulator (7), the head (G) of the testing system's manipulator (7) with bellows grippers (12) is mounted. Since the center of mass of the testing system's manipulator (7) is formed near its second end (G2), the second end (G2) of the testing system's manipulator (7) is affected by transverse forces, which are compensated by vertical crossbars (VS', VS"), i.e. the stability of the testing system's manipulator (7) is increased. One end of each vertical crossbar (VS', VS") is attached to the packaging production equipment's frame (R), at the horizontal crossbar (HS), through the upper additional crossbar (TM', TM'"). The other end of each vertical crossbar (VS', VS"), through the lower additional crossbar (TM", TM""), is fixed lower than the upper additional crossbars (TM', TM"), for example at such a distance from the upper additional crossbars (TM', TM'") that the lower additional crossbars (TM", TM"") are at or below the manipulator head (G) when viewed in a horizontal plane. The horizontal crossbar (HS) can also be implemented as a crossbar inclined at an angle to the horizontal plane, keeping the longitudinal direction of the the testing system's manipulator (7) substantially vertical.

Air distributors (2) distribute supplied air to the testing system, ensure its control, i.e., raising and lowering the bellows grippers (12), activating, and deactivating them, supplying air to the package (PK) for inspection. The air distributors (2) are attached to the horizontal crossbar (HS) of the first system mounting frame (1). Air distributors (2) are fixed on the horizontal crossbar (HS), on its opposite side to the testing system’s manipulator (7), behind the manipulator (7) or in the space between the testing system’s manipulator (7) and the vertical crossbar (VS'), between which and the manipulator (7) the packaging take-out unit (IL) is not positioned. Thus, the air distributors (2) are in such position that the air distribution hoses (not shown in the drawings) connecting the air distributors (2) to a pneumatic cylinder (5) of the testing system’s manipulator (7) and with distributor (14) of air to the grippers of the manipulator head (G), are located on other side of the testing system’s manipulator (7) compared to the package take out-unit (IL). For this reason, the area between the testing system’s manipulator (7) and the vertical mounting crossbar (VS"), between which the package take-out unit (IL) is positioned, is empty, safe, and convenient for positioning the package take-out unit (IL) and for transportation of packages (PK).

Pressure relays (3) are designed to measure relative pressure in packages (PK). They are attached to the horizontal crossbar (HS) of the first system mounting frame (1 ). The pressure relays (3) are fixed on the horizontal bar (HS), on its opposite side to the testing system’s manipulator (7), behind the testing system’s manipulator (7) or in the space between the testing system’s manipulator (7) and the vertical bar (VS'), between which and the testing system manipulator (7) the packaging take-out unit (IL) is not positioned. Thus, the pressure relays (3) are in such position that the air distribution hoses connecting the pressure relays (3) with the air receiver (6) and the testing system’s manipulator (7) with the air-supply-to- the-packages distributor (14), is located on other side of the testing system’s manipulator (7) compared to the package (PK) take-out unit (IL). For this reason, the area between the testing system’s manipulator (7) and the vertical mounting crossbar (VS"), between which the package take-out unit (IL) is positioned, is empty, safe, and convenient for positioning the package take-out unit (IL) and for transportation of packages.

The air receiver (6) is designed to store air of a certain pressure, which is later used to fill packages (PK) with pressure and to perform tightness test. The precision pressure regulator (9) can be attached to the air receiver (6) to adjust the air pressure supplied to the package (PK) being tested when high accuracy of the testing system is required. The air receiver (6) is installed independently of the package tightness pressure-testing system units: one, which comprise the first system mounting frame (1) and the elements installed on it; and the other, which comprise the mounting frames (31 , 34) of the unit (10) for cooling the bottom of the packages (PK) with the elements installed on it. The air receiver (6) is attached to the frame (R) of the packaging production equipment by using a separate mounting frame (K), which can be implemented as separate legs. The mounting frame (K) of the air receiver (6) is attached to the frame (R) of the packaging production equipment by using fasteners, such as bolts (V). It is desirable that the elements (V) for attachment of the air receiver (6) mounting frame (K) to the frame (R) of the packaging production equipment protrude through, between the mounting frame (K) of the receiver (6) and the frame (R) of the packaging production equipment and are locked. In this way, it is possible to install the units of the packaging tightness pressure testing system on the frame (R) of the packaging production equipment, in available place, without changing the design of the packaging production equipment.

The testing system’s manipulator (7) comprises the bracket (L) for fixedly attaching the testing system’s manipulator (7) at its one end (G1) to the first horizontal crossbar (HS) of the system mounting frame (1). The testing system’s manipulator (7) also comprises the pneumatic cylinder (5), the pneumatic cylinder's (5) holder (8) that is attached to the manipulator's holder (L), adjustment knobs (4), and the head (G) for gripping and testing the packages (PK).

The adjustment knobs (4) are designed to adjust position of the pneumatic cylinder (5) on the testing system’s manipulator (7), vertically up or down. The adjustment knobs (4) are mounted on other side of the pneumatic cylinder's (5) holder (8). The adjustment knobs (4) are also used to tighten the fasteners of the pneumatic cylinder (5) to the bracket (8). When adjusting position of the pneumatic cylinder (5), position of the gripper head (G) is adjusted at the same time in relation to the take-out unit (IL) for removal of the packages (PK) from the production equipment, considering the dimensions of the take-out unit (IL). The pneumatic cylinder (5) is intended for control of grip of the packages (PK) and the position of the testing head (G) in the vertical direction, i.e., for lowering to the package (PK) and lifting from the package (PK). The packages' (PK) gripping and testing head (G) comprises a universal flange (13), the distributor (14) of air to bellows grippers (12) and packages (PK), air distribution hoses (15), holder (11 ) for air-to-package distributor (14) and bellows grippers (12), and bellows grippers (12) for gripping and sealing the packages (PK). The universal flange (13) is designed to attach the head (G) for gripping and testing the packages (PK) to a piston rod (S') and to guiding rods (S) of the pneumatic cylinder (5).

The air distributor (14) is designed to distribute the air supplied to the bellows grippers (12). The air distributor (14) is formed of two parts (not shown in the drawings) and acts as a quick coupling. It allows quick disconnection of the entire testing head (G) without disconnecting couplers, hoses for air supply to the bellows grippers (12) and the packages (not shown in drawings). The air distributor (14) collects air in the first part of the distributor (14) and transmits it to the second part of the distributor (14), from which the air is discharged to the bellows grippers (12). The air distributor (14) serves a dual function: it helps transfer the supply air to the bellows grippers (12) and acts as a quick coupler when replacing the entire gripper head (G). By using the distributor (14), fewer pneumatic connections and pneumatic hoses are used.

Through the air distribution hoses (15), air is supplied: to/from the pneumatic cylinder (5); to/from bellows grippers (12) for their activation/deactivation; into the packages (PK) for tightness test. The holder (11) of the distributor (14) intended for distribution of air to the bellows gripers (12) and to the packages (PK), which also holds the bellows grippers (12), comprises first holes near periphery of the holder (11) in which the bellows grippers (12) are secured. It also comprises second holes through which at least part of the air distribution hoses (15) connecting the distributor (14) and the bellows grippers (12) are passed. It also comprises a central hole in which the air-to-gripper distributor (14) is fixed so that the connecting elements (X) of the hoses supplying air to the distributor (14) are located on the opposite side of the holder (11 ), which is the upper side compared to the connecting elements (Y) of the air distributor (14) for distribution of air to the bellows grippers (12) and the packages. The elements of the air distributor (14) for connecting the air distribution hoses (15) to the bellows grippers (12) are located on the lower side of the holder (11). Thus, a compact configuration of the gripping and testing head (G) is obtained, suitable for integration into limited working space. Each of the bellow grippers (12) for grabbing and sealing of package (PK) has a standard bellows gripper design and comprises a quick connect/disconnect first pneumatic coupling (18'), a piston (22), a package neck support (17), a package grabbing and sealing bellows element (19), such as the bellows, a shaft (23) for air introduction into the package, and an end plate (AT). The bellows gripper (12) also comprises a chamber (OK) into which air is supplied through a second pneumatic coupling (18") for activation of the bellows (19) of the gripper, or from which air is released through the second pneumatic connection (18") to release the bellows (19) and the package (PK) that is being held. Air for the tightness test is supplied to the package (PK) through the first pneumatic coupling (18') and the air supply shaft (23).

Depending on the bellows gripper's (12) size of belows (19) for gripping and sealing the package (PK), it is possible to grip packages with an internal diameter of the threaded part from 8 mm to 84 mm.

The package's (PK) gripping and testing head (G) can be configured with, for example, two or four bellows grippers (12), which would require an appropriate number of air distribution, transfer and regulation elements to connect in the system. For example, operation of one bellows gripper (12) requires such system elements as the pressure relay (3) to measure pressure, couplings (18', 18") and hoses (15). For four or more sockets, the quick coupler, similar to previously described quick coupler (14), should serve the middle two bellows grippers (12). For the end bellows grippers (12) there should be another coupler or a quick coupler, similar to previously described quick coupler (14), with more outlets and a holder (11') formed accordingly. Examples of implementation of the invention in the presence of more than two bellows grippers (12) are not detailed, since they are made in principle in the same way as the example of two bellows grippers (12) but using more elements of the air distribution and connection system.

The package-bottom-cooling unit (10), also being a support for bottom of the cooling packages (PK), comprises one frame (31 ), cold air supply means (32), cold air collector (33), mounting frames (34) for fixing cold air supply means (32) to the frame (R) of the package production equipment. The mounting frames (34) can be implemented as stands with magnetic mounting elements for mounting to the frame (R) of production equipment.

In all embodiments of the invention, the cold air collector (33), on which the packages (PK) brought by the take-out unit (IL) of the packaging production equipment are positioned, is fixed on an elongated rod (AR) for adjusting the position of the cold air collector (33) in vertical direction. The rod (AR) for adjusting position of the cold air collector (33) in vertical direction moves with a guide element (KR) of one mounting frame (31), which surrounds part of the adjustment rod (AR) around its entire circumference, along the entire length of the guide element (KR). The adjusting rod (AR) may, longitudinally, include angularly joined surfaces, which would cause the cross section of the adjusting rod (AR) to cover at least three angles. In all embodiments of the invention, cross-sectional shape of the adjusting rod (AR) corresponds to the shape of the cavity of the guide element (KR), through which the adjusting rod (AR) moves. The guide element (KR) also comprises means (UP) for locking the adjusting rod (AR) in the guide element. Thus, the cold air collector (33) is anchored and locked in a stable position in one mounting frame (31). One frame (31) for fixing the bottom cooling support (10) of the packages (PK) comprises two fixing branches (31', 31"), which are connected to the guide element (KR) from its sides so that from the guide element (KR) they would extend in opposite directions and extend in an essentially horizontal plane. Each branch (31', 31") comprises segments (TS\ TS") of fastening branches (31', 31") directed at an angle to the frame (R) of the packaging production equipment, at the ends of which means (FP\ FP") for fixing to the frame of the production equipment (R) are formed. Each means (FP', FP") for fixing the production equipment to the frame (R) comprises an elongate body, the shape of which corresponds to the shape of the surface of the component of the frame (R) of the production equipment to which the package cooling support (10) is attached, and end fastening means, such as screws extending through the production equipment frame (R) component and means (FP', FP") for fixing to the production equipment frame (R). The segments (TS', TS") of the fastening branches (31 ', 31") directed at an angle, preferably at a right angle, to the frame (R) of the packaging production equipment, are attached to segments (TS', TS") of said fastening branches (31', 31') at their free ends, in the central region of segments (TS', TS"). In this way, the support (10) for cooling the bottom of the packages (PK) is freely and stably attached to the frame (R) of the package production equipment, together with the first system mounting frame (1) holding the manipulator (7) of the testing system, so that packages (PK) delivered by the take-out unit (IL) of the package production equipment would be placed on the cold air collector (33) of the support (10) for cooling the bottom of the package (PK), under the bellows grippers (12), without additional adjustment of the position of packages (PK). The longitudinal central axis of each bellows gripper (12) corresponds to the central axis of the area (41) in which the package is placed on the cold air collector (33) of each respective package's (PK) bottom cooling support (10), which is perpendicular with respect to the cold air collector (33). In all embodiments of the invention, the cold air collector (33) is preferably a stainless-steel article, including connections (36) for supplying air to the collector (33). The collector (33) is formed with an internal cavity (not shown in the drawings), defined by a bottom (37) in which the connections (36) for air supply to the collector are formed, side walls (38) which surround the entire collector and are formed between the bottom (37) and an upper surface (39) in which holes (40) for supplying air to the packaging surface are formed. When the air is supplied to the cavity of the cold air collector (33), a pressure is created, which escapes through the perforated holes (40) directly towards the surface of the packages (PK). Perforated holes (40) are formed substantially concentrically above each of the air supply connections (36) to the collector (33). Each area (41) formed by the perforated holes (40) has a larger diameter than the diameter of the bottom of the package (PK), or at least the same as the diameter of the package (PK). With such an arrangement, the air flow surrounds not only the bottom of the package (PK), but also the side walls of the package (PK), up to the neck of the package (PK). The cavity of the cold air collector (33) can also be divided into separate cavities, each of which would comprise a connection (36) for air supply to the cold air collector (33) and an area (41) of perforated holes (40) formed above it. Thus, independent and uniform cooling of each of the packages (PK) would be ensured, when, for example, the positioning of the package (PK) over the perforated holes (40) would result in different conditions for air removal through the perforated holes (40), for example, different number of covered perforated holes (40) in each of the areas (41).

In all embodiments of the invention, each cold air supply means (32), such as a standard cold air gun, supplies compressed, filtered air to the cold air collector (33). The cold air collector (33) is provided at its bottom region (37) with connections (36) for connecting the cold air supply means (32) to the cold air collector (33) by means of air hoses (not shown). Preferably, each area (41) for positioning the packages on the cold air collector (33) is provided with a flow of cold air from a separate air supply means (32). Thus, adequate cooling of each package being tested would be ensured. Each cold air supply means (32) is attached to the frame (R) of the packaging production equipment by a separate mounting frame (34), such as a magnetic stand, which is fixed by means of the magnet on the paramagnetic element of the production equipment frame (R). Thus, the cold air supply means (32) can be attached to the frame (R) of the packaging production equipment in essentially any location, separate from the other main units of the system, such as the attachment of the support (10) for cooling the bottom of the packages (PK) to the frames (31, 34) of the production equipment frame (R), the attachment of the testing system’s manipulator (7) to the first frame (1) of the production equipment frame (R), or the attachment of the air receiver (6) to the frame (K) of the production equipment frame (R).

The integrable system for testing the tightness of plastic packages comprise separate mounting frames for the elements of the testing system (1, 31, 34, K), which allow the individual parts of the testing system to be attached to the frame of the packaging production equipment in integrated manner.

Example of tightness testing method:

The package is taken from its production mold present in the package production equipment, brought to the cold air collector (33) of the package (PK) bottom cooling support (10) of the tightness testing system and is placed on the cold air collector (33). Each package is designated to a separate area (41) of perforated holes (40) on which the package (PK) is placed. The pneumatic cylinder (5) lowers the package gripping and testing head (G) until the package (PK) neck rests against the support (17). The bellows (19) actuate and press to the neck of the package (PK) from inside, sealing it at the same time. Compressed air is supplied to the package (PK) through the opening in the bellows (19), where the pressure depends on the volume and geometric shape of the package. A pressure is created in the package (PK), for example, reaching 1.0-1.4 bar, which is maintained for a given period of time, for example, 0.3 seconds. In case of leak in the package, which implies a hole, the resulting pressure drop is recorded. If, for example, a pressure difference of 0.25 bar between the set and the measured pressures is noticed, a program gives an operator a message about a low-quality package, which can be automatically removed further down the line. The minimum pressure that can be measured by the sensors is, for example, 0.05 bar. The bellows grippers (12) release the package. The transport unit takes the packages out of the package production equipment. If substandard packages are identified, they are removed. During the tightness testing the bottoms and sides of the packages are cooled.

Cooling after molding helps to cool the packaging plastic faster, preserve the geometry, and improve the physical properties of the plastic. Parallel cooling during the tightness test ensures better physical properties of the bottle, and faster crystallization of the plastic after removing the bottle from the mold.

The control of the tightness testing system is carried out by a computer of the packaging production equipment. The measurement data of the integrated tightness measurement system is collected, interpreted, and visually presented on a control panel of a packaging production equipment.

Although the present description comprises numerous characteristics and advantages of the invention together with structural details and features, the description is given as an example of the invention embodiment. There may be changes in the details, especially in the form, size and layout of materials without departing from the principles of the invention, in accordance with the widely understood definition of terms used in claims.