WO2008128512A2 - Spread band mechanism - Google Patents

Abstract

The invention relates to a spread band mechanism comprising improved guidance of the spread band. Spread band mechanisms are used as machine elements for drive technology. The spread band mechanism according to the invention comprises a take-up roller for rolling up and unrolling the spread band. The spread band mechanism also comprises several rolling elements for the forced guidance of the spread band, said elements being located around the periphery of the spread band that has been rolled up on the take-up roller. Said rolling elements reduce the friction that occurs during the guidance of the spread band in comparison to guidance by a shoe according to prior art. The reduced friction leads to lower wear and thus to increased reliability and durability for the spread band guidance system.

Description

 Name of the invention

spread band

description

Field of the invention

The invention relates to a Spreizbandmechanik with improved guidance of the spreader. Spreader belt mechanisms are used as a machine element in drive technology.

A Spreizbandmechanik allows a transmission of tensile and compressive forces and bending moments to a limited extent by profiled metal bands. In this case, the stiffness property of a curved transversely to the winding direction metal strip is exploited, so that thus both tensile and compressive forces can be transmitted in the longitudinal direction of the belt, in contrast to the known Zugmittelgetrieben with metal bands. To transfer these forces to the drive rollers, the property of width variation of a curved band is used, which assumes its entire width in the wound state, while it is narrower in the developed and then curved in cross-section state. This change in width is used to clamp the band between the side windows (ribs) of the drive roller, whereby a positive and possibly positive connection is made. In its basic structure, a Spreizbandmodul consists of a role and a band and has a rotationally mounted, driven roller over two degrees of freedom in one plane. Forces can be transmitted via this basic structure only in the longitudinal direction of the belt, moments exclusively perpendicular to the longitudinal direction of the belt and to the axial direction of the roller. By combining several Spreizbandmodule that unite as a joint-member combination drive and guide member to parallel kinematics very compact robot can be built. These are characterized by a very good ratio of working space to building space as well as a comparatively simple mechanical structure.

A disadvantage of spreading band mechanisms is the high stress which the metal band is subjected to during the transition from the wound to the unwound stretched state. This is in particular given by the necessary clamping of the spreader between the two side windows of the drive roller.

Spreader belt mechanisms are known in which the side disks of the drive roller have a profiling in the circumferential direction and are biased in a targeted manner. As a result, the loads of the spreader are to be reduced and the power transmission can be made more efficient and accurate. However, even with this solution, the loads of the spreader are very high. The wear behavior of such a solution is not yet known. Another disadvantage of this solution is that a very accurate production of the side surfaces of the spreader is required in order to allow an improved power transmission. An increased positioning accuracy can only be achieved by complex control technology.

In a parallel patent application of the applicant Spreizbandmechana- are described in which the wound on a drive roller or a take-up reel spreader is passed through a sliding block. The sliding shoe enables defined winding and unwinding processes. Between the shoe and the spreader belt sliding friction occurs, which leads to high wear, especially at high speeds.

The object of the present invention is thus to provide an improved spreading band mechanism in which the stress of the expanding band is significantly reduced, in particular during the transition from the wound to the unwound stretched state, and at the same time a more efficient and precise force transmission is made possible. The improved spread-band mechanism should be distinguished by a high reliability, a long service life and a reduced production and maintenance costs.

This object is achieved by a spreading band mechanism according to the appended claim 1. The expansion band mechanism according to the invention initially comprises a spreading band, which can be reversibly converted from a stretched state into a winding state. In the extended state, the spreader has a profile in cross section. As a result, the spreader is suitable for receiving bending moments. However, if a part of the spreading belt has been transferred to the winding state, this part of the spreading belt has essentially lost its profile. This part of the spreading band is therefore flat in cross section. This transfer can take place continuously, so that the spreader can be transferred continuously in relation to its longitudinal direction in the winding state. This transfer is reversible, so that the spreader at any time back into the extended state is feasible, in which it has the profile again. The spreading belt mechanism according to the invention further comprises a take-up roll for rolling up and unrolling the spreading belt. That portion of the spreader, which is located between the winding roller and the stretched part of the spreader, undergoes a bending moment, by which the spreader at this position of the stretched state in the winding state is transferred. As a result, it loses its profile and is flat in cross section. The flat expansion band is now elastic enough to be rolled up on the take-up roll. This transfer takes place in the reverse direction, when the spreader is unrolled from the take-up roll. On the take-up roll large lengths of the spreader can be kept in a small space. Finally, the expanding band mechanism according to the invention has a plurality of rotatable rolling elements for positively guiding the spreading band, which are arranged circumferentially around the spreading band wound up on the winding roll.

Due to the rolling elements, the rolling friction occurring in the guidance of the expanding belt is significantly reduced in comparison with the sliding friction occurring in the case of a guide through a sliding shoe (according to the prior art). The reduced friction leads to less wear and thus to increased reliability and longevity of Spreizbandführung. The advantages of the Spreizbandführung invention are particularly clear at high speeds of the spreader, as it usually comes to increased forces between the spreader and its leadership. By the roller elements increased frictional forces between the spreader and its leadership are avoided. Thus, it does not overheat the spreader and the resulting wear.

The rolling elements may preferably be formed by rollers whose axes are parallel to the axis of the take-up roll. Alternatively, but also balls could be used, which press on the surface of the spreader and force it to rest on the take-up reel.

In a particularly preferred embodiment of the invention, the spreader mechanism has a plurality of rollers, which together form a roller conveyor. The roller conveyor surrounds the spreader belt rolled up on the take-up roll circumferentially completely or in sections. se, but with a Einfädelöffnung remains kept. Due to the roller conveyor, the guidance of the spreader belt is determined in the entire area of the take-up roll. The spreader is passed through the threading and can be wound on the take-up reel with very low friction and unwound from the take-up reel. The roller conveyor is arranged substantially circular, since it encloses the take-up roller circumferentially.

As an alternative to this embodiment, the expanding band mechanism according to the invention can be designed such that it has rollers for the positive guidance of the expansion band only in the transition region from the extended state to the winding state of the spreader belt. Outside this transition region, the spreader belt can be guided by a sliding shoe or the like.

The rollers are preferably urged by force on the wound on the take-up reel spreader. Consequently, the rollers can adjust in terms of their distance from the take-up reel of the amount of rolled up on the take-up reel spreader. The rollers can be urged, for example, by springs or actuators on the rolled-up on the take-up reel spreader. There is a larger amount of spreader on the take-up reel, so the radius of a spreader roll formed by the wound spreader is significantly larger than the radius of the take-up roll. If, on the other hand, there is little spread on the take-up roll, the radius of the take-up roll is barely greater than the radius of the take-up roll. The arrangement of the rollers is adapted to the ever-changing radius of the spreader roll formed by the wound spreader ribbon. In this embodiment of the spreading band mechanism according to the invention, it is ensured that the spreading band is guided in a defined manner in the region between the rollers and the already wound spreader belt. Otherwise it could come in this area to an uncontrolled transfer from the stretched state to the winding state, whereby the spreader would be unnecessarily stressed. In a preferred embodiment of the invention Spreizbandmechanik the roller conveyor is divided into several segments. The rollers are arranged in segments and thus also in segments urged onto the wound on the take-up reel spreader. The segmental construction of the roller conveyor simplifies the movable storage of the rollers, since not every roller is individually pushed onto the spreader roll wound on the take-up reel.

In a preferred embodiment, the segments each comprise a bracket on which the rollers of the respective segment are arranged. The brackets are each pivotally mounted relative to the winding roller and urged by a spring or an actuator against the wound on the take-up spreader. The roller conveyor can for example be divided into two segments, approximately 180 °, or three segments, approximately 120 °. The brackets then have approximately the shape of the corresponding circular segment and have bearings for the storage of roles. The brackets may each be rotatably mounted at one of its ends, wherein the spring or the actuator is formed by a compression spring which urges the bracket against the wound on the take-up reel spreader.

In a modified embodiment, the rollers of the segments are each connected flexibly to one another, so that the segments each form a roller chain. The roller chains are each stretched around a circular segment of the spreading belt roll formed by the wound spreader. The flexible roller chains can adapt to the variable curvature of the circumference of the spreader roll. This ensures that as many of the rollers of each segment roll on the surface of the Spreizbandrolle as possible. Furthermore, it is possible by the tensioning of the roller chains by one segment of the Spreizbandrolle effortlessly to urge the rollers on the wound on the take-up spreader. For example, the roller conveyor may be formed by two segments, each stretched by almost 180 ° of the circumference of the Spreizbandrolle are. The two roller chains can be stretched for example by a tension spring or an actuator.

The take-up roll is preferably drivable. The driving torque of the take-up roll is transferred during unwinding of the spreader due to the leadership by the rollers loss and precise as a thrust on the stretched part of the spreader. The take-up reel can also be braked or operated free-running.

The rollers are preferably designed as cylindrical needle rollers. The axes of all needle rollers and the take-up reel are aligned parallel to each other. All needle rollers are the same and have a length which is greater than the width of the spreader, so that the spreader is guided in its entire width, thereby a tape guide can be done by the rollers in the radial direction. A guide of the band in the axial direction can hereby preferably be accomplished by means of flat side windows, in particular two flat side windows.

Needle rollers can be arranged due to their small diameter at a small distance from each other, so that an accurate guidance of the spreader is possible. In modified embodiments, the running surface of the rollers can be adapted to a longitudinal profile or a remaining transverse profile of the spreading belt. It is also conceivable that the roller length is chosen to be smaller than or equal to the width of the spreader, in particular if no space is available laterally of the take-up reel.

The profile of the spreader is preferably formed by a simple curvature of the spreader. This profile shape of a spreader has proven to be the most suitable form for most applications. The spreading band mechanism according to the invention is, however, in principle also suitable for other profiles of the spreader belt. For example, are also wavy or triangular profiles usable. The expansion band may also have a profile in longitudinal section, for example in the form of holes or prongs.

The expansion band is preferably made of an elastic metal or an elastic plastic. Due to the elasticity of the spreader, this can be reversibly transferred from the stretched state to the winding state. Due to internal forces, the expansion band strives to take the profile and thus assume the stretched state. If a bending moment acts on the expansion band, the expansion band can initially withstand the bending moment due to the transverse profile. However, if the bending moment is greater than a transfer bending moment, then the expansion strip abruptly buckles at the point of action of the bending moment and loses its profile there. However, the non-profiled sections of the spreader belt can be deformed with lower bending moments, so that the spreader belt can be wound up. If the bending moment acting on the spreading band becomes smaller than a return bending moment, the expanding band resumes its profile and jumps into the stretched state.

In a preferred embodiment of the spreading band mechanism, the spreading band is wider in the winding state than in the stretched state. Due to the loss of the profile in the winding state, the spreader is flat and therefore wider. This property can be exploited, for example, for additional guidance in the take-up roll.

Further advantages, details and developments of the present invention will become apparent from the following description of a preferred embodiment, with reference to the drawings. Show it:

Fig. 1 is a schematic representation of a preferred embodiment of an expansion band mechanism according to the invention; Fig. 2 is a schematic diagram for illustrating the forces acting during winding forces; and

Fig. 3 is a schematic diagram illustrating the forces acting on the Ab-- ekeleln forces.

Fig. 1 shows a schematic diagram of a preferred embodiment of a spread tape mechanism according to the invention. The spreading band mechanism comprises a spreading band 01, which can serve as an actuator for positioning, for example. About the spreading 01 tensile and compressive forces, but also bending moments are transferable to a limited extent. At its proximal end, the spreading belt 01 is wound on a take-up roll 02. At the distal end, for example, a tool may be attached, which is to be positioned by the spreader.

The spreading band 01 is shown in two states. The portion of the spreading belt 01 which is wound on the take-up reel 02 is in a winding state. The other portion of the spreader belt 01 shown is in an extended condition. The spreading belt 01 is stretched in a straight line substantially rectilinear and has a curved profile.

In the winding state, the spreading belt 01 is flat in cross section and wider than in the extended state. It may have a curvature only rudimentary. The spreading belt 01 located in the winding state changes its shape in the longitudinal direction when bending moments occur, so that it can be wound onto the winding roller 02. The transition from the extended state to the winding state or vice versa takes place continuously during the winding or unwinding in the longitudinal direction of the spreading belt 01. On the periphery of a spread tape roll 03 formed by the rolled-up spreading belt 01, many needle rollers 04 are arranged. The spreader roller 03 is enclosed almost over its entire circumference by the needle rollers 04. However, the spreader roller 03 is not edged by the needle rollers in an area of a threading opening 06. The threading opening 06 serves to carry out the spreading belt 01, so that this can be wound onto the take-up reel 02, or unwound from the unwinding reel 02. All needle rollers 04 form a nearly circular roller conveyor. The needle rollers 04 are distributed on two segment bracket 07 of the roller conveyor. Each of the two segmental yokes 07 is rotatably mounted in a pivot point 08, so that the segmental yokes 07 can be pivoted in the direction of the take-up roller 02. Furthermore acts on each of the two segmental yoke 07 each have a compression spring 09, which urges the segmental bracket 07 in the direction of the take-up roll 02. This ensures that even then a large proportion of the needle rollers 04 is in contact with the surface of the spreader roller 03 when the Spreizbandrolle 03 is largely unwound and consequently has a reduced radius.

If the spreading belt 01 is moved in the direction of the take-up roll 02, it is pushed into the circular roller conveyor formed by the needle rollers 04, so that a bending moment acts on the transition region between the stretched section and the section in the winding state. As a result of the bending moment, the spreading belt 01 is continuously transferred into the winding state, whereby the bending moment is simultaneously reduced. This transition is continuous and continuous. By the circular guide, the expansion belt 01 winds on the take-up roll 02, regardless of whether the take-up roll 02 is driven and thereby exerts a tensile force on the spreading belt 01 or whether take-up roll 02 is free-running. Hg. 2 shows a schematic diagram for illustrating the forces acting during winding. This schematic diagram is based on the spreading band mechanism shown in FIG. 1, wherein for the sake of clarity the representation of individual features has been dispensed with. On the winding roller 02, a torque Mi acts, so that the spreading belt 01 is moved in a direction 11. The torque Mi acts counter to a tensile force F _z on the spreader belt 01. Starting from the spreader belt roller 03, radially outward, an individual force FR _{X is produced} , which results from the tendency of the spreader belt to assume the curved state. In contrast, the roller _belt of individual _forces F _{Px must act} on the surface of the spreader roller 03 in order to prevent the spreader belt from taking the curved state. The individual _forces F _Px give in their sum a force F _P which corresponds to a normal force F _N. The friction of the spreading belt 01 relative to the roller belt has a coefficient of friction μ. The spreader roller 03 has a radius r. Consequently, M ₁ = F ₂ ^• r + (M ^■ FN), the first summand corresponding to the drive torque and the second summand corresponding to the friction torque of the guided spread belt 01.

FIG. 3 shows a schematic representation for illustrating the forces acting on the wiper. This schematic diagram is again based on the spreading band mechanism shown in FIG. 1, wherein the illustration of individual features has been omitted for reasons of clarity. On the winding roller 02, a torque M ₁ acts, so that the spreading belt 01 is moved in a direction 12. The torque Mi acts counter to a thrust force F _s on the spreading belt 01. From the Spreizbandrolle 03 act single forces FRy on the roller belt. From the roller belt, individual forces F _{0x act} on the surface of the spreader roller 03. The friction of the spreader belt 01 with respect to the roller belt has a coefficient of friction μ. The spreader roller 03 has a radius r. Consequently, M ₁ = Fs T ₊ KM - FNH (M - FRy)]. LIST OF REFERENCE NUMBERS

01 spreading band

02 Take-up reel 03 Spreader roll

04 needle rollers

05 -

06 threading opening

07 Segment bracket 08 Fulcrum

09 compression spring, actuator

10 -

11 direction of the train bar

12 Direction of the Zuαbar

Claims

claims 1. Spreading band mechanism for transmitting tensile and compressive forces and bending moments, comprising: a spreading band (01) which has a profile in cross-section in a stretched state, wherein the spreading band (01) is continuously reversibly convertible into a winding state, in which the Spreizband (01) is formed flat transverse to the longitudinal direction; and - A take-up roller (02) for winding and unwinding of the spreading belt (01); characterized in that circumferentially around the on the Aufwickelrol- le (02) wound spreader (02) a plurality of rolling elements (04) for Guide the spreading band (01) are arranged, which are urged force loaded on the surface of the wound spreader. 2. Spreader mechanism according to claim 1, characterized in that it has a plurality of rollers (04) whose axes parallel to the axis of the take-up roll (02) and which together form a roller conveyor, which rolled up on the take-up roll (02) Spreizband (01) circumferentially encloses in an angular range of more than 180 °, wherein at least one Einfädelöffnung (06) is kept free of the roller conveyor. 3. Spreizbandmechanik according to claim 2, characterized in that the roller conveyor is divided into several segments, wherein the rollers (04) are arranged in segments and segment by segment on the take-up on the take-up roll (02) wound spreader (01) are urged. 4. Spreizbandmechanik according to claim 3, characterized in that the segments each comprise a bracket (07) on which the rollers (04) of the respective segment are arranged, wherein the bracket (07) are each pivotally mounted relative to the take-up roll (02) and are urged by a spring (09) or an actuator (09) against the spreader (01) wound on the take-up roll (02). 5. Spreizbandmechanik according to claim 4, characterized in that the rollers (04) of the segments are each connected flexibly to each other, whereby the segments are each formed by a roller chain, wherein the roller chains each formed around a circular segment by the wound spreader (01) Spreader roll (03) are stretched. 6. Spreizbandmechanik according to one of claims 1 to 5, characterized in that the take-up roll (02) is driven by a motor to a rotation. 7. Spreizbandmechanik according to one of claims 1 to 6, characterized in that the rolling elements are formed by needle rollers (04). 8. Spreizbandmechanik according to claim 1 or 6, characterized in that the rolling elements are formed by balls. 9. Spreizbandmechanik according to one of claims 1 to 8, characterized in that the expansion band (01) consists of an elastic metal or an elastic plastic. 10. Spreizbandmechanik according to one of claims 1 to 9, character- ized in that the spreading belt (01) changes upon application of a bending moment from the extended state to the winding state, wherein the acting bending moment is greater than a transfer bending moment. 11. Spreizbandmechanik according to one of claims 1 to 10, character- ized in that the spreader (01) is wider in the winding state than in the stretched state.