EP0652174A1

EP0652174A1 - Method of transporting an elongate flexible object, apparatus for carrying out said method and method of manufacturing comprising said method of transporting

Info

Publication number: EP0652174A1
Application number: EP93117892A
Authority: EP
Inventors: Christoph Schmitz (Nmn)
Original assignee: Procter and Gamble Co
Current assignee: Procter and Gamble Co
Priority date: 1993-11-04
Filing date: 1993-11-04
Publication date: 1995-05-10
Also published as: WO1995012539A1; CA2175037A1; KR960705729A; JPH09504499A; AU1043395A

Abstract

The invention relates to a method of transporting an elongate, flexible object, such as a belt, chain, wire or web, wherein the speed of a part of the elongate object Is periodically varied, while maintaining a constant speed of the upstream and downstream parts of the object. The method comprises feeding the elongate object (1) past transport members such as rotating transport rollers (13,15) which are oscillated parallel to the elongate object In the direction of transport and opposite to the direction of transport. Three sections (7a,7b,7c) of the elongate object are during oscillation of the transport members maintained In a mutually parallel relationship. Translation- and rotation balancing means allow the transport members to be driven at high speeds and low variations in torque.

Description

Field of the Invention

The invention relates to a method of transporting an elongate, flexible object along a stationary frame, the elongate, flexible object being transported along an upstream trajectory, a downstream trajectory, and an intermediate trajectory comprised between the upstream trajectory and the downstream trajectory, the method comprising the steps of:

a moving the elongate, flexible object along the upstream trajectory and along the downstream trajectory at a substantially constant speed of transport, the upstream and the downstream trajectory being substantially stationary relative to the frame,
b running the elongate, flexible object along a transport member that is periodically displaceable, the transport member having an upstream and a downstream part, and
c periodically displacing the transport member around a stationary equilibrium position.

The invention further relates to an apparatus for carrying out said method and to a method of manufacturing in which the speed of the elongate, flexible object is varied in accordance with said method.

Background of the Invention

Such a method and apparatus are known from EP-A-0 364 087.
In the above patent application, a device is disclosed for applying layers of material in a direction, generally transversely across a longitudinal web, which web moves continuously through the device in the machine direction at a predetermined web speed. The machine direction corresponds to the longitudinal direction of the web. The device comprises two transport members which each deflect the web through 90°, in the plane of the web. A transverse web portion of constant length, extending perpendicular to the machine direction, is comprised between the transport members, which are formed by air bars. The transport members are mounted on a cart which can be reciprocated in the machine direction.
When the transport members are moved in the transport direction of the web, at a speed which equals the web speed, the web portion between the transport members is stationary relative to the transport members. The transverse web portion is in this case stationary in the direction perpendicular to the machine direction, i.e. in the cross machine direction. An applicator, which moves in synchronism with the intermediate part of the web in the machine direction, can apply for instance strips of elastic material to the intermediate part of the web, without movement of the applicator in the cross-machine direction. These strips of elastic material extend in the transverse direction of the web.
Upon reversal of the movement of the transport members, the intermediate part of the web that extends between the transport members, is accelerated past the downstream transport member and is fed in the machine direction.
Although the above device is effective in changing the speed of only a predetermined portion of a web, the upstream and downstream parts being run at constant speed, the device introduces to the web portion a net speed component which is parallel to the direction of transport of the web. An applicator device is therefore necessary that moves with the speed of displacement of the air bars parallel to the transport direction, for the application of the transverse features to the web. This will complicate the applicator equipment and the device to supply the tape to the applicator.
Furthermore, for the web speed of the intermediate part of the web that is comprised between the transport members to become zero, the transport members need to be displaced at a speed that equals the web speed. Especially at high web speeds, the transport members will be subject to large accelerations.
Another disadvantage of the known device, is that the centre line of the downstream part of the web is displaced in the cross-machine direction, with respect the centre line of the upstream part of the web.
Furthermore, the above apparatus is not fit to be used in combination with a web which cannot be deflected into the cross-machine direction, such as a chain.
From US-A-4,399,905 an apparatus for forming a stack of articles is known, in which a flight of grippers are mounted on an endless belt. The belt is looped around transport a member, which is reciprocated so that a part of the belt is cyclically spatially stopped, at a continuous drive of the belt. By moving the transport member against the direction of transport of the belt, with the transport velocity, the speed of the belt relative to stationary frame of the stacker is stopped.
A disadvantage of the above apparatus is that the velocity of the transport member needs to equal the speed of transport of the belt for a part of the belt to become stationary. Furthermore, the path length of the part of the belt hat extends between the transport member and a stationary roller, changes upon reciprocation of the transport member. Hence, the known apparatus can only be used in combination with a chain or a toothed belt but not in combination with a flat web of relatively low strength.

It is an object of the present invention to provide a method of transporting an elongate flexible object, such as a belt, chain or wire, wherein the speed of a part of the belt chain or wire is varied while keeping the speed of the main upstream and downstream parts of the belt chain or wire constant.
It is another object of the invention to periodically vary the speed of a part of the elongate, flexible object at high frequencies, while keeping the speed of the main upstream and downstream parts of the elongate, flexible object constant.
It is another object of the invention to vary the speed of an elongate, flexible object, without causing a deflection of the object in the cross- machine direction.
It is again another object of the invention to vary the speed of an elongate, flexible object while exerting a low variation in tension on the object.
It is a further object of the invention to vary the speed of a part of an elongate, flexible object without causing movement of said part in a direction transverse to the direction of transport .

Summary of the Invention

The method according to the invention comprises running the elongate, flexible object along a guide member that is translationally stationary relative to the frame and along a transport member that is periodically displaceable, the transport member and the guide member each having an upstream and a downstream part.
A first section of the intermediate trajectory of the flexible elongate object extends between the upstream part of the guide member and the upstream part of the transport member.
A second section of the intermediate trajectory extends between the upstream and downstream part of the guide member or between the upstream part and the downstream part of the transport member.
A third section of the intermediate trajectory extends between the downstream part of the guide member and the downstream part of the transport member. The first and third sections of the intermediate trajectory are parallel to the second section of the intermediate trajectory.
When the transport member is reciprocated in a direction parallel to the second section of the intermediate trajectory, the lengths of the first and third sections of the intermediate trajectory are varied, while keeping constant the total length of the intermediate trajectory and while keeping constant the length of the second section of the intermediate trajectory.
Because of the constant length of the intermediate trajectory of the elongate, flexible object, which will hereafter be referred to as a " web", the time it takes for a part of the web to travel along the length of the intermediate trajectory is constant and is independent of the location of the intermediate trajectory relative to the stationary frame. Hence, the movement of those parts of the web that are located along the upstream and downstream trajectories, is not affected by the direction and the speed of the displacement of the intermediate trajectory relative to the frame. Therefore, by moving the intermediate trajectory of the web relative to the stationary frame, the speed at which the web travels along the intermediate trajectory can be adapted such that for those parts of the web that are located along the intermediate trajectory, the velocity relative to the stationary frame is increased, reduced, or reversed.
Relative to the stationary frame, the second section of the intermediate trajectory can be stationary or can be translationally displaced.
When the second section of the intermediate trajectory extends between a stationary upstream and a stationary downstream guide roller, the second section is stationary relative to the frame. An embodiment of the method according to the invention, in which the second section of the intermediate trajectory is stationary, is arrived at by passing the web along a path formed by an upper and a lower S-shaped loop. The bottom leg of the upper S-shaped loop is connected to the top leg of the lower S-shaped loop. The first and third sections of the intermediate trajectory correspond to the middle legs of the upper S-shaped loop and the lower S-shaped loop respectively. The second section of the intermediate trajectory corresponds to the combined bottom leg of the upper S-shaped loop and the top leg of the lower S-shaped loop.
Two stationary guide rollers are located in the bottom half of the upper S-shaped loop and the top half of the lower S-shaped loop respectively. Two transport rollers are located in the top half of the upper S-shaped loop and the bottom half of the lower S-shaped loop respectively.
The incoming web is fed from the upstream trajectory, past the upstream transport roller to the upstream guide roller, continues past the downstream guide roller to the downstream transport roller to the downstream trajectory. By moving the transport rollers in the transport direction of the incoming web at half the web speed, the incoming web is stored along the increased length of the top half of the upper S-shaped loop. The parts of the web that are located along the middle legs of the upper and the lower S-shaped loops, are then stationary relative to the frame.
By moving the transport rollers against the transport direction, the length of web that was stored along the top half of the upper S-shaped loop is accelerated along the second section of the intermediate trajectory, and is fed to the downstream trajectory of the web.
The first embodiment in which the second section of the intermediate trajectory is periodically translated relative to the stationary frame can be arrived at interchanging the positions of the transport rollers and the guide rollers in the above upper and lower S-shaped loop configuration. In this case, when the transport rollers are moved against the direction of transport of the incoming web at half the web speed, part of the incoming web is stored along the first trajectory, and part of the incoming web travels along the second trajectory at half the web speed, in the transport direction of the web. As the second section of the intermediate trajectory itself moves against the transport direction of the web, the position of the web relative to the frame is again stationary.
A preferred embodiment of the method according to the invention, in which the second section of the intermediate trajectory is translated, comprises feeding the web in a configuration which is formed by a first S-shape loop and a reverse S-shaped loop, which are connected in a back-to-back manner via their lower legs. The transport rollers are located in the lower halves of each S-shaped loop and the guide rollers are located in the top halves of each S-shaped loop.
The first and third sections of the intermediate trajectory correspond to the middle legs of both S-shaped loops and the second section of the intermediate trajectory corresponds to the combined lower legs of the S-shaped loops. The advantage of the above configuration, is that the upstream and the downstream trajectories of the web are located in the same plane and that the centre line of the downstream trajectory is not displaced.
It is essential in the method according to the invention, that the first and third sections of the intermediate trajectory are parallel to the third section. The term "parallel" is intended to include curvilinear trajectories, the perpendicular distance between which is constant. For instance, all sections of the intermediate trajectory may be located along straight lines, or the first and third sections of the intermediate trajectory may be located on segments of a first circle, the second section being located on a segment of a second circle, which is concentric with the first circle. Only when the parallel relationship between the first and third sections on the one hand, and the second section on the other hand, is maintained, will the total length of the intermediate trajectory be constant, independent of the position of the transport member.
By periodically varying the speed of the transport member with an amplitude of half the speed of transport of the web, the speed of the web relative to the frame periodically becomes zero, in three perpendicular directions. This allows operations to be performed on the web by applicator apparatus interacting with the web, the applicator apparatus being positionally stationary relative to the frame.
As the maximum speed of the transport members can be limited to half of the web speed, or less, in order to temporarily stop the web, the method can be applied at high web speeds, while maintaining the accelerations of the transport member relatively small.
In the method according to the invention, the centre lines of the upstream and the downstream parts of the web are not displaced in a direction parallel to the plane of the web. This allows the method to be used in production lines through which the web passes in a straight line, without having to realign the downstream part of the production line, or the use of an extra deflection member to realign the centre liner of the downstream part of the web. Longitudinal flexible objects, which are not flexible in a direction perpendicular to their length, such as chains, can be slowed down by the method according to the invention.
In an embodiment of the method according to the invention, the guide members and the transport members each comprise two rollers that are rotated by a drive means to reduce the strain exerted by the transport member on the web.
For a web of sufficient strength, pulling the web at constant speed of transportation past the reciprocating transport members, will cause the part of the web located along the second section of the intermediate trajectory to be periodically slowed down, to be stopped or to be reversed. In this case, the transport members and the guide members can comprise smooth cylindrical bars or air bars. When the elongate, flexible object is formed by a chain, the guide members can comprise sprocket wheels. For webs of relatively low strength, such as paper webs, tissue webs, fibrous batts or combinations thereof, driving of the transport rollers and the guide rollers assures exertion of a minimal strain on these webs. The guide rollers can be driven at a constant speed, such that their circumferential velocity corresponds to the transport velocity, V₀, of the web. The transport rollers need to be driven in synchronism with their periodic speed of displacement , V_T, so that their circumferential velocity varies periodically between V_o⁻V_T, and V_o+2V_T.
An apparatus for carrying out the method according to the invention comprises
a stationary frame ,
an upstream and a downstream cylindrical guide member connected to the frame in a translationally stationary manner, each guide member having an axis, the axes being generally parallel,
an upstream and a downstream cylindrical transport member, the axes of which are generally parallel to the axes of the guide members, the cylindrical surface of the upstream guide member and the upstream transport member being substantially tangent to a first plane, the cylindrical surface of the downstream guide member and the downstream transport member being substantially tangent to a second plane, which is substantially parallel to the first plane,and the cylindrical surface of the guide members or the transport members being substantially tangent to a third plane, located at a spaced apart location from the first plane and the second plane, and drive means connected to the frame for periodically displacing the transport members tangentially along a third plane which is parallel to the first and second planes, in a substantially straight line generally perpendicular to the axes of the transport members, around an equilibrium position located generally midway between the axes of the guide members, the distance between the axes of the transport members being constant.
When the third plane is located between the first and the second plane, the web is fed past the transport rollers in an upper and lower S-shaped loop configuration. The top leg of the lower S-shaped loop is connected to the bottom leg of the upper S-shaped loop.
In this configuration, the first section of the intermediate trajectory is located in the first plane which comprises the middle leg of the upper S-shaped loop. The third section of the intermediate trajectory is located in the second plane which comprises the middle leg of the lower S-shaped loop and the third section of the intermediate trajectory is located in the third plane which comprises the bottom leg of the upper S-shaped loop and the upper leg of the lower S-shaped loop.
In a preferred embodiment of an apparatus according to the invention, the first plane and the second plane are coincident, the intermediate trajectory being part of a double S-shaped loop comprising a first, inverted S-shaped loop and a second, S-shaped loop which are connected via their lower legs.
Preferably the transport members are mounted on a sled which is reciprocated along the frame.
An embodiment of the apparatus in accordance with the invention comprises rotation-balancing means which are rotationally coupled to the transport rollers, the rotation-balancing means being comprised of a two discs which are rotationally mounted on the frame. Each disc is linked to a pair of pulleys by a belt. The pulleys are connected to the sled on which the transport rollers are mounted, one pulley of each pair being driven by a respective transport member. A belt forms a closed loop around each disc and the respective pulleys. When the sled is reciprocated, the pulleys are translated within each closed loop of the balancing means, so that the speed of rotation of each disc differs in phase from the speed of rotation of the transport members by 180°, i.e. the speed of the discs increases when the speed of the transport members decreases and vice versa. This allows the combined transport members and balancing means to be run at constant torque by a drive motor driving the rotation balancing means and the transport members. Coupling of the transport members to balancing discs allows high speed movement of the sled, for instance at a rate of 550 rpm and a corresponding high rate of variation of the speed of the transport rollers.
A further embodiment of the apparatus according to the invention, comprises driving the guide rollers and the transport rollers by a single, endless drive belt or chain, a part of which runs parallel to the intermediate trajectory. By moving the part of the drive belt or chain that corresponds to the downstream trajectory of the web, at the constant speed of transport V₀_, the intermediate trajectory of the drive belt is run past the guide rollers with constant speed V₀, and past the transport rollers at a periodic speed of amplitude between V_o⁻²V_T, and V_o+2V_T.
Preferably the sled carrying the transport members, is suspended from the frame by a suspension means comprising two vertical arms, a lower end of each arm being connected to a respective end of the sled, each vertical arm being at its upper end hingingly connected to the frame.
Allowing the sled to swing on the frame obviates the need for linear bearings, and allows for reciprocation at relatively high speeds using a simple drive mechanism such as a reciprocating cantilever. Preferably the amplitude of reciprocation of the sled can easily be adjusted by varying the distance between the pivot point of the cantilever and the point of connection of the cantilever to the sled. The cantilever can be connected to a sled-balancing means to maintain a generally constant position of the centre of mass of the combined balancing means, the sled and the cantilever.
To ensure that the sled follows a substantially horizontal path of travel, rather than an arcuate trajectory, the sled is preferably suspended from the frame by means of a Evans linkage.
The method of apparatus according to the invention can advantageously be used in a manufacturing process, wherein an object is assembled or treated on a moving conveyor belt, the speed of the belt being varied at the position of a work station for execution of an assembly step or a processing step, without affecting the speed of the upstream and downstream part of the belt. Examples of such processes are found in assembly lines such as for microchips, cars, radios, packing lines such as for fillings of bags, bottles or boxes, automatic machining of a series of products, painting or printing or coating of a moving belt or web or objects placed thereon.
The method and apparatus according to the invention can especially be applied in the manufacturing of absorbent products wherein the elongate, flexible object is formed by a continuous web comprising a topsheet, a backsheet and an absorbent core of relatively low tear strength. The web is fed past an applicator station to have parts such as for instance elastic members, or a waist shield attached to it in a direction (cross machine direction) transverse to the feed direction. Temporarily stopping the web using the apparatus according to the invention, allows attachment of parts in the cross machine direction at high speed and low strain on the web, without the need for complex gripper means that move with the same speed as the web.
Another application of the method and apparatus according to the invention can be the application of a permanent deformation to the topsheet and/or the backsheet of an absorbent product using positionally stationary, corrugated members, to impart extensibility to the topsheet and the backsheet.

Brief Description of the Drawings

Figure 1 shows a schematic side elevational view of an embodiment of the apparatus according to the invention,
Figures 2a, 2b and 3 schematically show embodiments of an apparatus according to the invention, wherein the intermediate trajectory is translated,
Figure 4 shows the speed of the sled, transport rollers and web in the apparatus of figures 2a and 3,
Figures 5 and 6 schematically show embodiments of the apparatus according to the invention wherein the intermediate trajectory is translationally stationary,
Figure 7 shows the speed of the sled, transport rollers and web in the apparatus of figures 5 and 6,
Figure 8 shows a schematic perspective view of the apparatus according to the invention,
Figure 9 shows a schematic perspective view of the translation-balancing means and the rotation-balancing means,
Figure 10a and 10b schematically show the functioning of the rotation-balancing means
Figure 11 shows a side-elevational view of the translation-balancing means ,
Figures 12a-12d schematically show the functioning of the translation-balancing means,
Figure 13 schematically shows the functioning of the suspension means carrying the sled,
Figure 14 shows a perspective view of the drive mechanism for rotating the drive rollers and the guide rollers,
Figure 15 shows the apparatus according to the invention in an air-laying process for forming an absorbent core,
Figure 16 shows a schematic frontal view of a diaper manufacturing line comprising the apparatus according to the invention,
Figures 17a and 17b show schematic side views of the application means for imparting regions of extensibility to the web, and
Figure 18 shows a plan view of a diaper provided with regions of extensibiltiy using the apparatus of figures 17a and 17b.

Detailed Description of the Invention

Figure 1 shows an apparatus for transporting a flexible, elongate object 1. With flexible it is meant that the object 1 can be transported along a curvilinear trajectory and will adapt its shape so as to conform to the trajectory. The object 1 can be made of flexible material, such as webs made of paper, airfelt, plastic etc., or can be made of rigid segments that are hingingly linked in a chain-like manner. The elongate, flexible object can be two-dimensional, but can also be a one-dimensional structure, such as a wire, thread or rope.
The web 1 is transported along upstream trajectory 3 with a constant velocity of transport, V₀, in the machine direction F. The upstream trajectory 3 is formed by the length of the web 1 which extends to the right of the first guide member 9 in figure 1, and which is moving towards the infeed side 4 of the apparatus. After passing through the apparatus, the web 1 exits at the outfeed side 6 and is transported at constant velocity V₀ along the downstream trajectory 5, which extends to the left of the guide member 11. The upstream and the downstream trajectories need not correspond to the machine direction, and can be formed by straight-line or curvilinear paths.
The guide members 9 and 11 are cylindrical bodies such as smooth-surface bars or air bars, but are preferably formed by rollers which are rotationally connected to the frame 35. The guide rollers 9,11 have a fixed position. The web 1 is looped around an upstream and a downstream transport member 13,15 which are formed by rollers, that are mounted on a sled 41. The sled 41 is cyclically translated along the frame 35 around the equilibrium position 39, in a direction generally parallel to the machine direction F, by drive motor 36.
An intermediate trajectory 7a, 7b, 7c of the web 1 is located between the upstream guide roller 9 and the downstream guide roller 11, and comprises a first section 7a and a third section 7c, of variable length, located between the upstream guide roller 9 and the upstream transport roller 13 and the downstream transport roller 15 and the downstream guide roller 11 respectively. The second section 7b of the intermediate trajectory is located between the transport rollers 13 and 15 and is of constant length.
Because of the symmetry of the intermediate trajectory 7a, 7b, 7c, the increase in length of the first section 7a, upon displacement of the sled 41 opposite to the machine direction F and away from the equilibrium position 39, is compensated by an equal decrease in length of the third section 7c, and vice versa. As the length of the second section 7b is constant, the whole intermediate trajectory 7 is of constant length. Hence the time for the web 1 to travel past the intermediate trajectory 7a, 7b, 7c is independent of the position of the sled 41 with respect to the frame 35.
When the part of the web that is located along the second section 7b of the intermediate trajectory 7a, 7b, 7c, is stationary relative to the frame 35, the web 1 is contacted by applicator means 29, 29' , 38, 38' which are positionally stationary with respect to the frame 35. The applicator means comprise a pair of vertically displaceable tampers 29, 29' which press the web 1 against the lower parts 38, 38' of the applicator means. After the applicator means have interacted with the web 1, the web is accelerated along the section 7b of the intermediate trajectory towards the outfeed side 6 of the apparatus 2, and is supplied to the downstream trajectory 5 with web speed V₀.
The guide rollers 9,11 and the transport rollers 13,15 are driven by a drive member in the form of a closed loop 50 and pulleys 52,53 and 54. The loop 50 is partly parallel to the intermediate trajectory 7a, 7b, 7c. The loop 50 is driven at a constant speed which is equal to the speed of transportation, V₀, of the web 1 by a single drive motor 51. By driving the guide rollers 9,11 and the transport rollers 13,15, the strain exerted on the web 1 is minimised and can be limited to the acceleration forces, which are acting to change the speed of the web.
Figures 2a,2b and 3 illustrate embodiments in which the intermediate trajectory 7a, 7b, 7c is translated with respect to the stationary frame 35. In the embodiment of figure 2a, the guide members 9,11 and the transport members 13,15 are arranged in a double S-shaped loop in which a left-hand, reverse S-shaped loop comprising the downstream guide roller 11 and the downstream transport roller 15, is connected via its bottom leg to a right-hand S-shaped loop comprising the upstream transport roller 13 and the upstream guide roller 9.
In the embodiment of figure 2b, the sled 41 comprises two pairs of transport rollers 13,13' and 15,15'. The intermediate trajectory 7 comprises the part of the web 1 which is located between upstream guide roller 9' and downstream guide roller 11'. The web 1 is stationary relative to the frame 35 along section 7b of the intermediate trajectory 7 when the sled 41 moves against the direction of transport, F, with a velocity of V₀/4. The addition of n pairs of guide rollers to the frame 35 and n pairs of transport rollers to the sled 41, allows the speed of the sled 41 to be reduced to V₀/2n to stop the motion of the web 1 along section 7b. Hence, the web 1 can be run at a relatively high speed , while maintaining the speed of the sled 41 relatively low, although the construction of the sled becomes more complicated upon addition of extra pairs of transport rollers.
In the embodiment of figure 3, the transport members and the guide members are configured in an upper and lower S-shaped loop. Upon displacement of the sled 41 in the upstream direction (opposite to the direction of transport, F), parallel to the sections 7a,7b and 7c, the first section 7a of intermediate trajectory is elongated. Generally the direction of displacement of the sled 41 will correspond to the direction of transport, F, in which the web 1 is transported towards the input side 4 of the apparatus. However, as is indicated in figure 2a, the web 1 can be transported towards the input side 4 and away from the output side 6 at any desired angle, the direction F' being for instance vertical as indicated by the broken lines in figure 2a.
A part of the incoming web is stored along the increased length of section 7a. The parts of the incoming web that cannot be accommodated along the increased length of section 7a, slip past the upstream transport roller 13, via the downstream transport roller 15 and guide roller 11 to the downstream trajectory 5 . At the downstream side, the section 7c is shortened by the same amount by which section 7a is increased. The length of web located along the decreased length of section 7c is also passed to the downstream trajectory 5.
When the sled 41 moves against the direction of transport F at a speed V_T, the increase in length of the section 7a in a predetermined time interval, is proportional to V_T m. In the predetermined time interval, the length of incoming web 1 is proportional to V₀ m, wherein V₀ is the constant velocity of transport of the web 1 along the upstream and downstream trajectories 3, 5. The rate at which the web slips past the upstream transport roller 13 in the direction of transport, is equal to V₀-V_T, which is the relative speed of the web 1 with respect to the sled 41 and the transport rollers 13,15. As the sled 41 moves at a speed V_T against the direction of transport, the relative velocity of the web,V_W, relative to the stationary frame 35 is equal to V₀-2V_T.
At the downstream side, the decrease in length of section 7c is proportional to V_T m. This length of web is supplied to the downstream trajectory 5. Also supplied to the downstream trajectory 5 is the length of web, slipping past the transport rollers, 13, 15 which is proportional to V₀-V_T m, so that the total length supplied in the pre-determined time interval to the downstream trajectory 5 is proportional to V₀ m. Hence, the velocity of the web 1 along the downstream trajectory 5 remains unaltered, and is independent of the speed V_T of the sled 41.
It follows that if the sled 41 moves against the transport direction F, at a speed equal to half the speed of transport of the web 1 ( $V_{T} =V₀/2$
), the web 1 travels along the second section 7b of the intermediate trajectory 7 at the same speed at which the section 7b is moved along the frame 35. Hence, the net displacement of the web along the second section 7b, relative to the stationary frame 35, is zero. If the sled 41 moves against the transport direction at a speed V_T which is slower than half the speed of transport, V_o/2, the web 1 is slowed down relative to the frame 35, along the second section 7b of the intermediate trajectory 7a, 7b, 7c. If the sled 41 moves at a speed, V_T, faster than half the speed of transport, V_o/2, the speed of the web along the second section 7b of the intermediate trajectory 7 is reversed relative to the stationary frame 35, and is directed against the transport direction. F.
Upon reversal of the speed of the sled 41 in the direction of transport F, the length of section 7a is in a pre-determined time interval shortened by a length which is proportional to V_T m . This length of web, as well as a length proportional to V₀ m of incoming web, travels past section 7b of the intermediate trajectory 7. As section 7b itself travels at V_T m/s past the frame 35, the speed of the web 1 , V_W,relative to the stationary frame 35 equals V₀+2V_T in the direction of transport, F. At the downstream side, the section 7c has increased by a length which is proportional to V_T m in 1 s. This length of web, as well as a length proportional to V₀ m that is to be transported to the downstream trajectory 5, needs to be supplied past downstream transport roller 15. Hence the speed with which the web needs to be supplied past the downstream transport roller 15, corresponds to the speed of the web along section 7b (V₀+V_T m/s) .
In figure 4 the speed of the web 1 relative to the stationary frame,V_W, along the second section 7b of the intermediate trajectory 7, has been graphically indicated for a cyclical speed of the sled 41, V_T , with an amplitude V₀/2, equal to half the velocity of transport. The speed of the web relative to the second section 7b of the intermediate trajectory 7 has been indicated as V_R . V_R corresponds to the circumferential velocity of the transport rollers 13 and 15. It can be seen that the speed of the web V_W along section 7b, relative to the stationary frame, is in phase with the speed V_T of the sled 41 and varies around the constant speed of transport V₀ between 0 and twice the constant speed of transport. The circumferential speed of the transport rollers is also in phase with the speed of the sled 41 and varies around V₀ between V₀/2 and 3V₀/2.
Figures 6 and 7 show embodiments of the apparatus 2 in which the second section 7b of the intermediate trajectory 7 is translationally stationary relative to the frame 35.
Moving the sled 41 in Figure 5 in the transport direction F at half the speed of transport, causes the upstream trajectory 3 and the section 7a to be increased in length. The incoming web 1 is stored along this increased length, so that the speed of the web along section 7b is stationary. At the same time, the downstream trajectory 5 and the section 7c are shortened, and the parts of the web that were located along these sections are supplied to the downstream trajectory 5.
Reversal of the movement of the sled, causes the web that was located along the increased lengths of the upstream trajectory 3 and section 7a, to be accelerated along section 7b to the downstream side 5.
The embodiment of the method and apparatus as shown in figure 6 works according to the same principles as the embodiment of figure 5. In figure 6, the sections 7a and 7c of the intermediate trajectory 7, are located on a first cylindrical surface along transport roller extension means 55, 57. The second section 7b of the intermediate trajectory 7 is located on the surface of a drum 59. Upon moving of the sled 41 concentrically with the axis 61 of the drum 59, in an anticlockwise direction, the lengths of the section 7a and the upstream part of section 7b are increased. The lengths of the downstream side of section 7b and the third section 7c are decreased in length such that the combined length of sections 7a and 7c as well as the length of section 7b is constant.
When the transport rollers 13,15 are moved with the sled 41 in a pre-determined time interval along a section of the circumference of the drum 59 which is proportional to half the velocity of transport, about half the incoming web is stored along the increased length of section 7a and about half the incoming web is stored along the increased upstream part of section 7b. The velocity of the web along section 7b, relative to the frame is constant.
In figure 7, the web speed,V_W along section 7b and the circumferential speed V_R of the transport rollers 13, and 15 are given for cyclic displacement of the sled 41 along a trajectory concentric with the axis 61 of the drum 59, with a velocity V_T having an amplitude of half the speed of transport of the web. The circumferential speed of the transport rollers is indicated as V_R . When the drum 59 is rotationally connected to the frame, the circumferential speed of the drum will correspond to the web speed,V_W . The velocity and phase relationships of Figure 7 also apply to the embodiment of Figure 5.
Figures 8 and 9 show a perspective view of the embodiment of the apparatus in which the guide rollers 9,11 and the transport rollers 13,15 are rotationally mounted on the sled 41. The sled 41 is suspended from the frame 35, which has been schematically indicated in these figures, by suspension means 79,79'. The sled 41 is driven by a cantilever 71, which is pivotably connected to the sled in a drive point 73. The transport rollers 13,15 are connected to rotation balancing means 63,63' which allow the transport rollers to be driven at a constant torque. In the embodiment of figure 8, the rotation balancing means drive a rotating balancing mass 62 via a closed loop member such as belt or chain 64. The balancing means rotate with the same rotational velocity as the transport rollers to which they are connected, and are simultaneously translated within the closed loop member 64. As a consequence the balancing mass 62 is rotated in synchronism with the transport rollers but in the opposite direction to the direction of rotation of the transport rollers. Hence the resultant torque of the balancing mass 62 and the transport rollers 13,15 is constant.
In a preferred embodiment of the invention, the rotation balancing means 63,63' each comprises a disc 65, 65' which is rotatably connected to the frame 35. This is shown in figure 9. For each disc 65, 65' two pulleys 67,69 and 67 and 69' are mounted on the sled 41. A belt 70,70' is looped around the balancing disc's 65, 65' and the pulleys 67, 69, 67', 69'. The pulleys 69,69' are each coupled to the axes 25,27 of the transport rollers, 13,15. The circumferential speed of the pulleys 69,69' is equal to V_R.r/R wherein r is the radius of the pulleys 69,69' and R is the radius of the transport rollers 13,15.
The functioning of the balancing means 63,63' as shown in figure 9 has been schematically indicated in figures 10a and 10b. In figures 10a and 10b, the position of the sled 41, has been indicated at its equilibrium position 39 in solid lines and at a position close thereto, in broken lines.
When the sled 41 is furthest from its equilibrium position 39 (a position which has not been indicated in figures 10a and 10b),the sled 41, and with it the pulleys 67,69, are translationally stationary. The stationary positions of the sled 41 can for the embodiments of figures 2a, 2b and 3, be found in figure 4 at positions 0, T/2 and T of the x-axis. For a stationary sled 41, the belt 70 is driven by pulley 67 such that the circumferential speed of the disc 65 in this case is equal to the circumferential speed of the pulley 67. When the speed of the sled 41, V_T, is zero, it can be seen from figure 4 that the circumferential speed of the transport rollers, V_R, is equal to the speed of transport, V₀ . For the case in which the radii of the pulleys 69, 69' are equal to the radii of the transport rollers 13,15, the circumferential speed of the disc 65 equals V₀.
When the sled 41 is close to its equilibrium position, and is moved in the direction of transport, F, from the position indicated by the broken line in figure 10a, to the position indicated by the solid line in Fig 11a, the speed of the sled approximately equals V₀/2. This situation can be found around time T/4 on the x-axis of figure 4. When pulleys 67 and 69 are in a pre-determined time interval displaced by a distance proportional to V₀/2, a length of belt 70 proportional to V₀ (the broken-line part at the right-hand side in Figure 10a) needs to be transported past pulley 69 to pulley 67 to take up the slack. No rotation of the disc 65 is necessary. However, as can be seen from Figure 4, the rotational speed of the transport rollers and the pulleys that are driven by the transport rollers, equals 3V₀/2. Therefore, in addition to the length V₀ of belt 70 that is moved past the pulleys 67 and 69 upon translation of the pulleys, an additional length V₀/2 of belt 70 needs to be supplied to pulley 69 by rotation of the belt 70 past the disc 65. Hence the rotational speed of the disc 65 is proportional to V₀/2.
When the sled 41 is close to its equilibrium position, and is moved against the direction of transport F, , the speed of the sled again about equals V₀/2. This situation is found around time 3T/4 on the x-axis of Figure 4, and is illustrated in Fig 10b. Considering again a displacement of the pulleys 69 and 67 proportional to V₀/2 in a predetermined time interval, it can be seen that a length of belt 70 which is proportional to V₀ needs to be taken up by rotation of disc 65. From figure 4 it can be seen that the speed of the pulley 69, which is driven by the transport roller 15, equals V₀/2, so that in the given time interval an additional length of belt 70, proportional to V₀/2, is accumulated at the upstream side of pulley 67. Therefore, in addition to the length proportional to V₀ that is to be passed from pulley 67, via the disc 65, to pulley 69, the pulley 67 supplies a length of belt 70 to disc 65 which is proportional to V₀/2 . Hence the speed of rotation of the disc 65 is proportional to 3V₀/2.
As appears from the foregoing discussion, the rotation of the disc 65 varies with the same frequency as the transport rollers 13,15 and with a fixed 180° phase difference with the speed of rotation of the transport rollers 13,15. Only when the radii of the pulleys 69, 69' are equal in length to the radii of the transport rollers 13,15 will the amplitudes of the circumferential speed of the disc 65 be equal to the speed of the transport rollers, V_R. By adapting the mass distribution of the discs 65 to the moment of inertia of the transport rollers, the overall variations in torque of the combined transport rollers 13,15 and the discs 65, 65' with respect to an axis of the drive motor 51 , can be minimised. Hence the drive motor 51 will not be adversely affected by the high -frequency changes in rotational velocity of the transport rollers.
Figure 11 shows a side-elevational view of the sled-balancing means 77, which is formed by a rotating mass balance that comprises two rotating balancing masses 80,81. The sled balancing means 77 comprises a housing 87 having an inner circular track 85. The housing 87 is attached to the frame 35, and is stationary with respect to the frame. The cantilever 71 is at its upper end connected to the balancing masses 80 and 81.
Rotating mass 80 compensates the inertia forces that are exerted on the cantilever 71 by the sled 41, such that the sled, the cantilever and the balancing means can in combination be driven at a constant force. The sled 41 performs a horizontal periodic motion, and is accelerated and decelerated by the cantilever 71. The sled 41 exerts a periodic force on the cantilever 71 that is proportional to the acceleration and that is largest when the speed of the sled is 0. The horizontal component of the force exerted on the cantilever 71 by the rotating mass 80 is also periodic and has the same frequency as the frequency of reciprocation of the sled 41, is equal in magnitude to the force exerted by the sled and is directed in the opposite direction. The mass 80 is driven, for instance by a drive shaft 84, at a constant rotational speed. The vertical component of the force exerted by the mass 80 on the housing 87, is compensated by the mass 81, that travels up and down along straight-line path A-C.
The mass 81 is mounted on a disc 83, having a diameter equal to half the diameter of the circular track 85. The disc 83 is rotationally mounted inside the housing 87 and travels along the circular track 85. The disc 83 may be formed by a pinion, the circular circumference 85 being provided with meshing gear teeth. The position of the balancing mass 81 and the disc 85 at position B of the circular track 85, have been indicated in Figure 11 in broken lines. Further rotation of the disc 85 to position C of the circular track 85, will move the centre of mass MB along the line AC from the centre of the circular track 85 to point C. Further rotation of the disc 83 via position D, back to A, moves the centre of mass MB back along line AC to position A.
In figures 12a-12d it is schematically illustrated how the mass balancing system 77 interacts with the sled 41. The housing 87 comprising the circular track 85 is connected to the frame 35 and is stationary with respect thereto. A drive shaft 84, which extends perpendicular to the plane of the drawing and which passes through the center of the circular track 85, rotates the mass 80 at a constant rotational speed. The disc 83 is at its center rotatably connected to the mass 80 such that upon rotation of the mass 80, the disc 83 is rotated along the track 85.
Upon rotation of the disc 83 along the track 85, the points of the circumference of disc 83 that are located in positions corresponding to point A and to the center of the track 85 in figure 12a, move along straight-line paths, that are diametrically located with respect to the circular track 85.
The cantilever 71 is connected to a linkage 88 which is hingingly connected to the circumference of the disc 83 in a point J which in figures 12a and 12c coincides with the center of circular track 85. The drive shaft 84 drives the mass 80 and the disc 83 at a constant rotational speed. As shown in figures 12a and 12c, the sled 41, which has been schematically indicated, is in its equilibrium position. Since the sled 41 is suspended from the frame 35 via the Evans linkage (which has not been shown in figures 12a-12d) the sled does only exert horizontal inertia forces on point J. As the acceleration of the sled 41 is 0 in its equilibrium position, no horizontal forces are exerted by the sled on point J in this position. The vertical force exerted on the housing 87 by the rotating mass 80, is in this position compensated by the force exerted by the mass 81, which is accelerated towards the center of circular track 85.
Upon rotation of the disc 83 in the direction of arrow Q, the point J moves along a straight-line path from the center of the track 85 to point B. The balancing mass 81 moves from position A to the center of track 85. When the cantilever 71 and the sled 41 reach their maximum deflection and the sled is to accelerating in direction of arrow Fs, the horizontal inertia force exerted by the sled on point J is at its largest and is directed opposite to the direction of arrow Fs. The horizontal component of the force exerted on the housing 87 by rotating mass 80 is also at is maximum value and is directed in the direction of arrow Fb, and compensates the force exerted on the point J by the sled 41.
The mass 81, which in Figures 12b and 12c has been indicated by the broken lines, is located in the center of circular track 85, and moves at maximum, constant speed. Hence, no inertia force is exerted by the mass 81 on the housing 87.
Upon further rotation of the disc 83, the mass 81 reaches point C, reverses its direction of straight-line movement, and travels back to the center of track 85, as has been shown in figure 12c. The forces acting on the housing 87 and point J in figure 12c and 12d are identical in magnitude and opposite in direction to the forces that act in the position of the sled 41 as shown in figure 12a and 12b respectively.
The weight of the balancing masses 80,81 and he distances of the balancing masses from the drive shaft 84 will depend on the actual configuration of the sled 41 and the cantilever 71, and can on the basis of the above principles easily be determined. The principle of the mass-balancing of the sled 41 is also applicable to constructions, in which the cantilever 71 is driven by other means than the rotating drive shaft 84.
The suspension means 79,79' as shown in figures 9 and 10 comprise a Evans linkage, the principle of which has been schematically indicated in Figure 13. In the Evans linkage, a vertical suspension arm 89 is suspended in rotation point 97. The sled 41 is suspended at the lower end 96 of the suspension arm 89. Rotation of the vertical suspension arm 89 around the rotation point 97, causes the lower end 96 of the arm 89 to follow a circular rotation path 101. In order to have the lower end of the arm 89 move along a straight-line path 105, the centre of rotation 97 needs to be displaced upon rotation of the arm 89. The suspension arm 89 is thereto connected to a rotation arm 86, which in figure 13, for the vertical position of the suspension arm 89, is located behind the suspension arm. The rotation arm 86 is rotatable around rotation point 95 , and positions 91 and 94 of the rotation arm 86 have been indicated . The length of the rotation arm 86 is of generally half the length of suspension arm 89.
When the rotation arm 86 is moved to position 91, the lower end of the suspension arm 89 can be located on circular path 106 which is indicated by a broken line. The lower end of the suspension arm 89 will be located on straight-line path 105 for position 91 of the rotation arm 86 when the upper end of the suspension arm 89 is moved vertically downwards. The upper end of the suspension arm 89 is in a hinging point 108 connected to a transverse arm 93. As the transverse arm 93 is of relatively large radius, and the angle of rotation of the arm 93 is relatively small, the path of the hinging point 108, which is part of the circular path 103, approximately corresponds to the vertical displacement of the upper end of the arm 89.
Via the suspension means 79, the sled 41 can be reciprocated along a substantially straight line path 105 without the need for linear bearings. This allows the sled to be reciprocated at a high speed without intensive maintenance requirements to the bearings of the suspension means.
Figure 14 shows a perspective view of the drive mechanism for rotating the guide rollers 9,11 and the transport rollers 13,15 in accordance with the speeds as shown in figures 4 and 7. The drive member 50, which is comprised of a belt, is passed around drive rollers 110,112, 114 and 116, along a path which is parallel to the web 1. The drive rollers 110 and 114 are equal in diameter to the guide rollers 9 and 11, and rotate at a constant velocity V₀ which corresponds to the velocity of the upstream and the downstream parts of the web 1. The drive rollers 112 and 116 are equal in diameter to the transport rollers 13 and 15, and rotate with a cyclic speed of amplitude V₀/2 around the speed of transport V₀ . The belt 50 is passed along pulleys 113 and 111 and forms a closed loop. The pulley 113 is driven by a drive motor, 51, at a constant speed V₀. Due to the reciprocation of the transport rollers 13,15, the belt 50 passes along these rollers at the above cyclic speed. The belt 50 drives the guide rollers 9,11 at the constant speed V₀.
The method and apparatus according to the invention can be applied to a wide variety of processes in which a belt, chain or wire is moved at a constant speed and in which a part of the process involves a manipulation of the belt, chain or wire, or of objects carried thereby, at a different speed.
The object which is transported can for instance be a chain or belt which is transported in an endless loop at a constant, average speed and which passes through the apparatus according to the invention. In this case, the guide rollers and the transport rollers need not be driven. The chain or belt can be part of a drive mechanism or gear system for a further apparatus. The guide members and transport members need not be cylindrical, but can for instance be of polygonal cross-section.
The chain or belt can comprise gripping means that project from the sides of the chain or belt, and which are displaced in the cross machine direction relative to the guide rollers and the transport rollers to be able to pass along side the transport rollers and the guide rollers, rather than between them. At the position of the applicator means, 38 the objects carried by the belt or chain can be combined with other objects, assembled, packed, machined, painted, printed or otherwise treated.
The apparatus and method according to the invention are particularly suited for transporting objects of a relatively weak tear strength such as paper webs or fibrous cellulosic diaper cores, and changing the speed of these objects at high frequencies without any strain being exerted on these objects. The paper webs can be stopped to be printed or painted at the applicator means 38.
For the diaper cores, which comprise batts of fluff pulp that are comprised between a liquid impervious backsheet and a liquid pervious topsheet the cores can be slowed down at the applicator station for different purposes.
The applicator means can comprise nozzles for deposition of absorbent gelling material onto the fibrous batt. If the absorbent gelling materials are deposited at a constant rate, varying the speed of the batt past the nozzles results in a longitudinal variation of the absorbent gelling material in the diaper cores. Applicator means for supplying absorbent gelling material are described in US-A- 4, 523, 274 issued to Maulder et al. on September 24, 1985 and European Patent EP-B- 0 380 675.
In a core-forming process for air-laying a batt of cellulosic fibers, the apparatus can be configured as shown in figure 15. The fibrous batts 190 can be transported on a foraminous belt, 178 which is passed by the apparatus according to the invention. The applicator means can comprise a vacuum suction box, 180 carrying the batts past the transport rollers and the guide rollers and a fiber lay down chamber 192 located above the vacuum suction box. The speed of the foraminous belt 178 can be varied to be adapted to the rate of deposition of the fibres onto the foraminous belt. The speed of fibrous batt 190 in the fiber lay-down chamber 192 can for instance be decreased as more fibres are deposited onto the foraminous belt and the rate of deposition decreases.
Figure 16 shows a schematic frontal view of the apparatus 2 according to the invention and the applicator means 38 for applying a pre-stretched strip of elastic material 161, such as a laminate elastic material, to the web 1, such as for instance a waistband or waistcap 154. The direction of transport of the web 1 is perpendicular to the plane of the drawing. The elastic material 161 is unwound from a roll by a metering element comprising two rolls 159, 160. Roll 159 is driven at slower speed than roll 160 , so that the strip of elastic material is pre-stretched. The elastic material is fed along an automatic tracking system 162 to minimise variations in the position of the center line of material 161 at the metering point that is located at the infeed point of the rotating vacuum belt 163. A glue coater 164 intermittently coates the elastic material with a continuous, or spiral-patterned layer of glue. The pre-stretched elastic material 161 is tightly held on the perforated conveyor 165 by action of vacuum suction box 166 . The rotating conveyor 165 passes the elastic material by a crush knife 167, and subsequently rotates the elastic material in a parallel position to the web 1. The web is stopped by the apparatus 2, and the air cylinders 29,29' as shown in figure 1 push the web 1 against the elastic element 161. Each air cylinder comprises a tamper foot. After a short dwell-time (a few milliseconds), the air cylinders 29, 29' are moved upwards, the web 1 is accelerated in the direction of transport. Upon actuation of the air-cylinders 29,29', the vacuum acting on the pre-stretched elastic material is switched of by means of a mechanical switch, blocking the access of the apertures in the conveyor 167 to the vacuum suction box 166. The movement of the transport rollers 13,15, the mechanical vacuum switch of the vacuum suction box 166 , the air cylinders 29,29' the glue coater 164 and the knife 167 are all synchronised to maintain the proper phase relationship between the different movements.
Figure 17a shows an embodiment in which the applicator means 38,38' comprise a pair of corrugated members 170, 171 having intermeshing teeth, for physically deforming the web. 1. When the corrugated members 170, 171 are clamped down on the web 1, the web is deformed along parallel lines, corresponding to the corrugations which in this case extend perpendicular to the plane of drawing. The web has increased extensibility in the direction perpendicular to the lines of the deformations, the web 1 being after contacting with the corrugated members 170, 171 elongatable in a harmonica-like fashion. By stopping the web 1, relative to the corrugated members 170, 171, a complex pattern of deformation can be applied to the web which pattern has a component in the transverse direction of the web, so that the web is elongatable in the machine direction. Using the apparatus according to the invention makes it is possible to provide the leg portions 172 of the diaper, as is indicated in Fig 18, with increased extensibility. Preferably, an elastic element is comprised between the topsheet and the backsheet of the diaper in its relaxed state in the areas of deformation. Prior to contacting the web with the members corrugated 170, 171, the web 1 can not be substantially elongated. After contacting the web with the corrugated members 170, 171 , the areas of the web 1 in which the elastics are located are activated, and become elastically extensible.
The physical deformation can also be applied in the longitudinal direction of the web 1, for instance in the area of the side panels 158, or the waist areas, 173, 175 as shown in figure 18.
A known method for applying physical deformations to impart extensiblity to a web is commonly referred to as "ringrolling". Ringrolling involves passing the moving web between the nip of two rollers that are provided with circumferential corrugations. The axes of the rollers extend in the cross-machine direction of the web. Another form of "ringrolling" involves the use of flat corrugated members, of the type shown in Figs. 17a and 17b of the present application. The above method, as well as structures produced thereby have been described in detail in US-A-5,196,000 issued to Clear et al. on March 23, 1993; US-A-5,167,897, issued to Weber et al. on December 1, 1992; US-A-5,156,793, issued to Buell et al. on October 20,1992, in particular Figure 5, in combination with the description, Column 20; and US-A-5,143,679, issued to Weber et al. on September 1,1992.
The method and apparatus according to the invention allow slow-speed deformation of the web 1. Hence the impact-times of the corrugated members on the web can be longer so that the physical deformation can be better dimensionally controlled and the energy imparted to the web can be more gradually distributed.
The apparatus according to the invention can be used to provide complex deformation patterns to products of the type described in the above patents. The physical deformation imparted by the method and apparatus according to the invention, can be so configured to impart extensibility to the whole of the absorbent product, such as the combined topsheet, backsheet and core, or to only portions thereof, such as to the lateral wings of a sanitary napkin as described in US-A-4,687,478, issued to Van Tilburg on August 18,1987.

Claims

Method of transporting an elongate, flexible object (1) along a stationary frame (35), the elongate, flexible object (1) being transported along an upstream trajectory (3), a downstream trajectory (5), and an intermediate trajectory (7a, 7b, 7c) comprised between the upstream trajectory and the downstream trajectory, the method comprising the steps of:
a moving the elongate, flexible object (1) along the upstream trajectory (3) and along the downstream trajectory (5) at a substantially constant speed of transport, the upstream and the downstream trajectory (3,5) being substantially stationary relative to the frame (35)

b running the elongate, flexible object (1) along a guide member (9,11) that is translationally stationary relative to the frame (35) and along a transport member (13,15) that is periodically displaceable, the transport member (13,15) and the guide member (9,11) each having an upstream and a downstream part,
such that:
- a first section (7a) of the intermediate trajectory (7a, 7b, 7c) of the flexible elongate object (1) extends between the upstream part (9) of the guide member (9,11) and the upstream part (13) of the transport member (13,15),

- a second section (7b) of the intermediate trajectory (7a, 7b, 7c) extends between the upstream part and the downstream part of the guide member (9,11) or between the upstream part and the downstream part of the transport member (13,15), and

- a third section (7c) of the intermediate trajectory (7a, 7b, 7c) extends between the downstream parts (11,15) of the guide member (9,11)and the transport member (13,15),
the first section (7a) and the third section (7c) of the intermediate trajectory (7a, 7b, 7c) of the elongate, flexible object, (1) being parallel to the second section (7b) of the intermediate trajectory (7a, 7b, 7c)

c periodically displacing the transport member (13,15) relative to the guide member (9,11) around a stationary equilibrium position (39) in a direction substantially parallel to the second section (7b) of the intermediate trajectory (7a, 7b, 7c) of the elongate, flexible object (1), while keeping constant the length of the intermediate trajectory (7a, 7b, 7c) and while keeping constant the length of the second section (7b) of the intermediate trajectory (7a, 7b, 7c)
Method according to claim 1, wherein the periodic speed at which the transport member (13,15) is moved relative to the guide member (9,11) has an amplitude of 1/2n times the speed of transport, so that the elongate flexible object (1) along the second section (7b) of the intermediate trajectory (7a, 7b, 7c) is periodically stationary with respect to the frame (35), wherein n is a natural number.
Method according to any of the previous claims, the transport member (13, 15) comprising two transport rollers which are rotated by a drive means (50,51) such that the strain exerted by the transport member (13,15) on the elongate, flexible object (1) is reduced.
Method according to any of the previous claims, the guide member (9,11) comprising two guide rollers that are driven by a drive means (50,51) such that the strain exerted by the guide member (9,11) on the elongate, flexible object (1) is reduced.
Method according to claims 3 and 4, the guide rollers (9,11) and the transport rollers (13,15) being driven by a drive belt or drive chain running along the guide rollers (9,11) and the drive rollers (13,15) generally parallel to the intermediate trajectory (7a, 7b, 7c) of flexible object (1).
Method according to any of the previous claims, the transport rollers (13,15) being connected to a balancing means 63, 63', such that variations in torque exerted by the transport rollers are reduced.
Method according to claim 6, the transport rollers (13,15) and the balancing means (63,63') being driven in combination, at constant torque.
Method according to any of the previous claims, the transport member (13, 15) being connected to a translation balancing means (77), the combined centre of mass of the transport member (13,15) and the translation-balancing means (77) being kept substantially stationary.
Apparatus (2) for carrying out the method according to any of claims 1 to 8, the apparatus comprising:
a stationary frame (35),
an upstream and a downstream guide member (9,11) connected to the frame (35) in a translationally stationary manner, each guide member (9,11) having an axis (19,21), the axes (19,21) being generally parallel,
an upstream and a downstream cylindrical transport member (13,15), the axes (25,27) of which are generally parallel to the axes (19,21) of the guide members (9,11), the cylindrical surface of the upstream guide member (9) and the upstream transport member (13) being substantially tangent to a first plane (29), the cylindrical surface of the downstream guide member (11) and the downstream transport member (15) being substantially tangent to a second plane (31) which is substantially parallel to the first plane (29), and the circumferential surface of both guide members or both transport members (13,15) being substantially tangent to a third plane (33) which is located at a spaced apart location from the first plane (29) and the second plane (31) and which is parallel thereto,
and drive means (36, 71) connected to the frame (35) for periodically displacing the transport members (13,15) generally perpendicular to the axes (25, 27')of the transport members, around an equilibrium position (39) located generally midway between the axes (19,21) of the guide members (9,11), the distance between the axes (25, 27) of the transport members being constant.
Apparatus (2) according to claim 9, wherein the first and the second plane (29,31) are coincident, a distance between the axes (25, 27) of the transport members (13,15) being larger than a distance between the axes (19,21) of the guide members (9,11) and wherein the transport members (13,15) are displaceable along a substantially straight line.
Apparatus (2) according to claim 9, wherein the first and the second plane (29,31) are coincident, a distance between the axes (25,27) of the transport members (13,15) being smaller than a distance between the axes (19,21) of the guide members, and wherein the transport members (13,15) are displaced along a circular path.
Apparatus (2) according to any of the previous claims, the two transport members (13,15) being connected to a sled (41) which is mounted on the frame (35) so as to be movable relative to the frame (35).
Apparatus (2) according to claim 12, the transport members (13,15) being rotatable around their axes (25,27), each transport member being mechanically coupled to a rotation-balancing means (63, 63') comprising a rotatable disc (65, 65'), the phase of the rotational speed of which differs by 180°, or a whole multiple thereof, from the phase of the rotational speed of the transport members (13,15), so that the transport members(13,15) and the balancing means (63,63') in combination can be rotated at a constant torque.
Apparatus according to claim 13, the rotation-balancing means (63, 63') comprising for each transport member (13,15) a rotatable disc (65,65') which is fixed to the frame (35), and for each disc (65,65'):
- two pulleys (67,69; 67',69') connected to the sled (41), one pulley (67,67') being driven by a respective transport member (13,15) and

- a belt (70,70') fed around the circumference of the disc (65,65') and around both respective pulleys (67,69; 67',69') to form a closed loop.
Apparatus according to any of claims 12, 13 or 15, the sled (41) being suspended from the frame (35) by a suspension means (79,79') comprising two vertical arms (89,89'), a lower end (96,96') of each arm (89,89') being connected to a respective end of the sled (41), each vertical arm (89,89') being at its upper end hingably connected to the frame (35).
Apparatus according to claim 15, the upper end of each vertical arm (89,89') of the suspension means (79, 79') being connected in a hinging point (108, 108') to a first side of a transverse arm (93,93'), the transverse arm (93,93') being at a second side hingably connected to the frame (35), each vertical arm (89,89') being hingingly connected at its midpoint (97,97') to an upper end of a further vertical arm (86,86') that extends generally parallel to the vertical arms (89,89') and has a length generally half of the length of the vertical arms(89,89'), a lower end of the further vertical arms (86,86') being hingably connected to the frame (35).
Apparatus according to any of claims 9 to 16, the guide members (9,11) and the transport members (13,15) each being rotatable around their axes, the apparatus comprising a drive member (50) which is run along the guide members (9,11) and transport members (13,15) to form a closed loop a part of which extends parallel to the intermediate trajectory (7a,7b,7c) and a drive motor (51) driving the drive member (50) at a constant speed and a constant direction of rotation.
Apparatus according to any of claims 9 to 17, the drive means (36,71) comprising a reciprocatable cantilever (71), connected to the frame (35) in a pivot point (75), the cantilever (71) being connected to the sled (41) in a drive point (73).
Apparatus according to claim 18, a distance between the pivot point (75) and the drive point (73) being adjustable.
Apparatus according to any of claims 9 to 19, the sled (41) being connected to a translation-balancing means (77) to maintain a generally constant position of the centre of mass of the combined translation-balancing means (77), the sled (41) and the transport rollers (13,15).
Method of assembling an object comprising at least two components, the method comprising the steps of:
transporting a first component of the object in accordance with the method of any of claims 1 to 8, and
contacting the second component with the first component when the first component is at the second section (7b) of the intermediate trajectory (7a, 7b, 7c).
Method according to claim 21, characterized in that the first object if formed by the elongate, flexible object.
Method according to claim 21, characterized in that the first object is transported by the elongate, flexible object.
`Method according to claim 22, characterized in that the first object comprises a paper web, a fibrous batt, a liquid-pervious topsheet, a liquid impervious backsheet or a combination thereof.
Method according to claim to 24, the method including in a diaper - manufacturing process any of the following steps or combinations thereof:
- applying an adhesive to a web,

- applying a tape fastening system to a web,

- applying an absorbent gelling material to a web,

- applying a waist features to a web,

- applying a reinforcement strip to a web or

- imparting an increased extensibility to a web or to a part thereof.
Method of applying a material to an elongate flexible object (1), or to an object transported thereby, the method comprising the steps of
- transporting the elongate, flexible object in accordance with the method of any of claims 1 to 8, and

- applying the material the intermediate position of the elongate, flexible object when the elongate, flexible object is at the second section (7b) of the intermediate trajectory (7a, 7b, 7c), from an applicator means (38,38') which is positionally stationary relative to the frame (35).
Method of treating a moving elongate, flexible object (1), or an object placed thereon, the method comprising the steps of
- transporting the elongate, flexible object (1) in accordance with the method of any of claims 1 to 8, and

- treating the elongate, flexible object (1) or the object placed thereon at the second section (7b) of the intermediate trajectory (7a,7b,7c) with a treatment means which is positionally stationary relative to frame (35).