Chain drive unit

A chain drive unit (4, 5, 6) for reducing chain vibrations comprising a chain wheel unit (43) with at least two sprockets (431, 432) that are arranged parallel on a common rotation axle, at least two parallel chains (51, 52) engaging these sprockets (431, 432). At least one damping element (6) connecting two adjoining chains (51, 52). The circumferential orientation of two adjoining sprockets (431, 432) differs by a partial pitch (pP) and the damping element (6) comprises a first fixation (61) on its one free end for the lateral fixation to the first chain (51), a second fixation (62) on its opposite free end for the lateral fixation to the second chain (52) and a force transmission unit (63, 8, 9) arranged between the first and the second fixation transmitting an applied force from the first fixation (61) to the second fixation (62) and vice versa.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of priority under 35 U.S.C. 119 of European Patent Application EP 13196063.5, filed Dec. 6, 2013, the entire disclosure of which is hereby incorporated by reference herein, in its entirety and for all purposes.

TECHNICAL FIELD

The present invention relates to a chain drive unit, in particular for a roller chain, with at least one driven chain wheel, chains engaging said chain wheels and at least one damping element for damping chain vibrations.

BACKGROUND

The drive unit for lifting systems usually comprises wires, tooth belts or chains.

Chain drives become acoustically or physically noticeable when the chain is caused to vibrate. The most common cause for such vibrations is the so called polygon effect that occurs, when the drive wheel engages with the chain in a form-fit. Since the chain cannot continuously roll-on or -off the drive wheel, angular offsets of the chain occur, so that the drive wheel forms a polygon. As a result, vibrations in the longitudinal and the transversal direction of the chain occur.

Usually, to prevent these vibrations, chains with a small pitch, chain wheels with an increased number of teeth or other means like wires, tooth chains or tooth belts are being used. In comparison to roller chains, tooth chains are very expensive and tooth belts have a limited life time.

SUMMARY OF THE DISCLOSURE

It is therefore a task of the current invention to provide a simple, easy to install and cost-effective damping element that suppresses the undesired vibrations of a chain drive.

This task is solved by a chain drive unit with the features of claim1, a damping element with the features of claim9and a method with the features of claim10.

Chain drives, especially for lifting units, for security reasons, must comprise two chains, each of which being able to carrying out the lifting on its own. The current invention uses the existence of the second chain to its advantage.

Usually there are two chains per chain drive unit, in some cases; more than two chains are indicated. In the cases, where there are more than two chains, the following is true for each pair of adjacent chains. The general expression chain includes simplex-, duplex-, triplex- or other multiplex-chains.

The chain drive unit for damping chain vibrations according to the invention comprises a chain wheel unit with at least two sprockets that are arranged parallel on a common rotation axle, at least two parallel chains engaging these sprockets and at least one damping element connecting two adjoining chains.

The circumferential orientation of two adjoining sprockets differs by half a pitch, if there are two chains in total. If there are three chains, the difference between two adjoining sprockets is a third of a pitch. In general, the circumferential orientation of two adjoining sprockets differs by a partial pitch. The partial pitch being defined by one divided by the number of sprockets times a sprocket's pitch.

In cases with more than two sprockets, for example three, the sprockets can be arranged as such that the difference between the first and the second and the second and the third sprocket is a third of a pitch. Alternatively, the sprockets can be arranged as such that the difference between the first and the second sprocket is two third of a pitch and the difference between the second and the third sprocket is one third of a pitch. However, the sum of all the absolute partial pitches is an integer. The absolute partial pitch of a specific sprocket being defined by the difference between the circumferential orientation of the first sprocket compared to the one of the specific sprocket.

By doing so, the vibrations in the adjoining chains are out of phase with one another. In the case with two sprockets, the angular phase shift is 180 degrees and in the case with three sprockets 120 degrees. In general, the angular phase shift is 360 degrees divided by the number of sprockets.

In the case with multiplex-chains, the above-stated is true between two adjoining multiplex-chains and their corresponding sprockets.

In the case with two sprockets, the distance between two adjoining teeth, when considering both chains, is only half a pitch. In order to achieve this with a single tooth wheel, the pitch would have to be halved, which would lead to smaller teeth, which would lead to a smaller load capacity.

With the design according to the invention, a smaller effective pitch, while maintaining the individual pitch and the individual tooth size of each chain wheel is obtained.

The damping element comprises a first fixation on its one free end for the lateral fixation to the first chain, a second fixation on its opposite free end for the lateral fixation to the second chain and a force transmission unit arranged between the first and the second fixation transmitting an applied force from the first fixation to the second fixation and vice versa. The force transmission unit can comprise a single element or a plurality of elements.

This design allows the use of simple elements that can be easily attached to the chains, without its life time being restricted by friction wear. The purpose of these elements is to transmit forces from one chain to an adjoining one in a distributed manner along the chain length. The position and the distance between two adjoining damping elements may differ depending on the applied load, the chain's speed and length and type.

Preferably, the position of the first fixation on one of the chains differs to the position of the second fixation on the other chain in a longitudinal direction of the chain's movement by a sprocket's pitch (P) divided by the number of sprockets or by a multiple thereof. Preferably, for a uniform distribution in general, the position of the first fixation differs to the position of the second fixation by (the number of sprockets*n+1) times the partial pitch (pP). Preferably, in the case with two sprockets, the position of the first fixation differs to the position of the second fixation by half a pitch (P) or by (2*n+1) times half a pitch, wherein n is an integer. With this design, identical fixations can be used on either of the two adjoining chains, which is easier in manufacturing. However, as an alternative, damping elements with non-identical fixations can be used in order to realise a difference of the first fixation to the second fixation of zero or a multiple of a pitch. However, any other irregular distribution is also possible.

Preferably the distance between these two positions is half a pitch, one and a half pitch or two and a half pitch. Bigger distances are thinkable but are more likely to cause problems when moving around the chain wheel. The different distances between these two positions allow the use of different damping elements with different behaviour. For example, a longer element might be more flexible than a shorter one or a stronger element can be used while maintaining the flexibility of a corresponding weaker element.

Preferably the force transmission unit comprises arc-shaped leaf springs or magnets or tension or pressure springs.

The leaf spring design has the advantage that the force transmission unit can be produced as a single piece from the same material as the two adjoining fixations. Deviations from the original distance between the two positions of the fixations as well as angular deviations when circling around the chain wheel are absorbed by the leaf spring.

A force transmission unit with magnets provides a touch-less connection between the two fixations. On each of two adjoining chains, a magnet is fixed to said chain, while the magnet being fixed to the first chain does not contact the one being fixed to the second chain, allowing a damper to “float” on the chain pivot points, eliminating stress while passing through the sprockets. This is advantageous in view of the positional and angular deviations, as the magnets simply move away from one another and no additional stress is induced.

The design with the tension or pressure spring is a valuable alternative to the leaf spring. Although being more complex, these springs have a very high life time in view of fatigue.

Independent from the embodiments, the damping element can be installed in various directions, transmitting longitudinal and/or lateral forces from the first chain to the adjacent second chain. In one embodiment, all damping elements have the same orientation, i.e. all the force transmission units are oriented parallel to or opposite to the longitudinal direction. In another way, different damping elements have a different orientation, i.e. some of the force transmission units are oriented parallel to the longitudinal direction and some are oriented opposite to the longitudinal direction.

Also independent from the embodiments are the number of damping elements per chain drive unit and the spacing between two adjoining damping elements. Preferably there is a damping element every tenth to hundredth pitch, more preferably every thirties to seventieth pitch, more preferably every fiftieth pitch.

In a preferred embodiment, the first fixation comprises a first clip with two opposing clamping jaws for clamping an outer link plate of the first chain and a second clip with two opposing clamping jaws for clamping an outer link plate of the second chain. The clamping jaws provide a simple and secure means for clamping the damping element to the chains. Alternatively, damping elements with only one clamping jaw can be used or the fixation is attached to the chains by means of a magnet or by means of a combination of a clamping jaw and a magnet.

Preferably, the damping element further comprise a flap on its free ends adjacent to the first and second clamping jaws for abutting against an adjacent pin of the corresponding chain. These flaps on either free end of the damping element control the engagement of a clip with a corresponding link plate by providing a tension that holds the damping element in place securely and additionally provide a means for transmitting a force from one chain to the other one.

In another preferred embodiment, the first and second fixation comprises at least one magnet reception with a shoulder, a corresponding pin reception and a corresponding magnet. The pin reception is adapted to receive a pin from the first chain and is aligned with the corresponding magnet reception that is adapted to receive the corresponding magnet. The magnet reception comprises a shoulder, on which the magnet rests. The pin reception can form a single recess together with the magnet reception or they can be separate from one another. The magnet reception is conically widening towards the outside, allowing the magnet to be inserted easily. The magnet, on both cases, can be in contact with the pin or can be arranged at a distance thereto.

In such an embodiment, the force transmission unit comprises a common housing comprising the first and second fixation. In order to compensate for some relative movement in the longitudinal direction between two adjoining chains, there is some clearance in the pin reception between the pin and the walls of the pin reception surrounding said pin. As the connection between the magnet and the pin is not fixed, some relative movement in the lateral direction between two adjoining chains is compensated in that the magnet moves away from the pin.

In a preferred embodiment, the chains are roller chains. Alternatively link chains with torus-shaped links might be used.

Preferably, a lifting system using a chain drive unit according to the invention further comprises a holding frame with guiding elements arranged thereon for the guiding of a lifting element arranged thereon and a weight compensation, wherein the lifting element is connected to the weight compensation by means of the chain drive unit.

The holding frame ensures a solid fixation to the surrounding and provides a solid base for the lifting element. Depending on the application, the frame is installed vertically or inclined. Such a holding frame allows a versatile application of this system.

Using a weight compensation to compensate the weight of the lifting element allows the use of a smaller drive, as only the additional weight of goods to be conveyed or people to be transported needs to be moved by said drive.

In a preferred embodiment, the chain drive unit is arranged on top of the holding frame. This design is advantageous as an open chain can be used that is on one side connected to the lifting element and on the other side connected to the weight compensation. The chain is guided over and supported by the chain wheel unit, providing a simple and easy to install system. Alternatively, the chain drive unit can be installed at the bottom or the middle of the holding frame or even adjacent to it together with a chain that forms a closed loop.

Preferably, a damping element to be used in a chain drive unit comprises a first fixation on its one free end for the lateral fixation to the first chain, a second fixation on its opposite free end for the lateral fixation to the second chain and a force transmission unit arranged between the first and the second fixation transmitting an applied force from the first fixation to the second fixation and vice versa.

Newly built or existing lifting systems can be equipped with a chain drive unit according to the invention by providing a chain wheel unit with at least two sprockets whose circumferential orientation differs by half a pitch, providing a chain unit with at least two parallel chains whose member's positions differ by half a pitch, providing chain fixation elements for attaching a lifting element on one free end of the chain unit and a weight compensation on the opposite free end thereof and providing at least one damping element that comprises a first fixation on its one free end for the lateral fixation to the first chain, a second fixation on its opposite free end for the lateral fixation to the second chain and a force transmission unit arranged between the first and the second fixation transmitting an applied force from the first fixation to the second fixation and vice versa.

Further embodiments are stated in the dependent claims.

DETAILED DESCRIPTION

FIG. 1shows a perspective view of an embodiment of a lifting system1according to the invention. The lifting system's1main components are a holding frame2, a lifting element3, a chain drive unit comprising a drive unit4, a chain unit5and damping elements6, and a weight compensation7.

The holding frame2comprises a side frame21on either side of the frame, the side frames21being mounted on a lower cross connection22serving as a base plate to fix the holding frame2on the ground and connecting the side frames21to one another in the lower region of the holding frame2. The holding frame2further comprises upper cross connections23connecting the side frames21to one another in the upper region of the holding frame2. The upper cross connections23serve as a base for the arrangement of the drive unit4. Sideways and outward facing guiding means211are mounted on each of the side frames21for guiding the lifting element3.

The lifting element3comprises a lifting frame31that is connected to the holding frame2by guiding means211. In this embodiment, the lifting frame31in essence, is L-shaped, its vertical arm being in sliding contact with the holding frame2and its horizontal arm forming a base for a platform or a cabin.

The drive unit4comprises a drive plate41a drive42mounted on said drive plate41and a chain wheel unit43mounted in line with said drive42on side drive plate41and connected to said drive42for transmitting a rotational movement generated by the drive42via said chain wheel unit43to the chain unit5engaging said chain wheel unit43. The drive unit4is mounted on the holding frame2by means of the drive plate41.

The chain unit5, in this embodiment, as can be seen inFIGS. 2 to 5, comprises a first chain51and a second chain52and damping elements6,6a. The chains in this embodiment are roller chains, comprising inner link plates511,521, outer link plates512,522, pins513,523and rollers514,524. The longitudinal direction L is defined by the direction of the movement of the chains51,52and is indicated with an arrow L inFIG. 2. As can be seen inFIG. 2, the members of the first chain51with respect to those of the second chain52are offset to each other by half a pitch P.

The damping elements6,6aare fixed to an outer link plate512of the first chain51by a first fixation61and are fixed to an outer link plate522of the second chain52by a second fixation62. Additionally, a first flap64adjoining the first fixation61abuts on an adjoining pin513protruding the outer link plate522of the first chain51, the first fixation61is attached on and a second flap65adjoining the second fixation62abuts on a corresponding pin523of the second chain52.

The difference between a first embodiment of a damping element6, as shown inFIGS. 2 and 3, and a second embodiment of a damping element6a, as shown inFIGS. 4 and 5, is the different distance in the longitudinal direction L of the first fixation61to the second fixation62. The distance of the first embodiment is half a pitch P and the one of the second embodiment is one and a half pitch P.

FIGS. 6 and 7show a chain wheel unit43of a drive unit according to the invention. The chain wheel unit43comprises a first sprocket431, a second sprocket432and a spacer435, all being arranged on a common rotation axle. Each of the sprocket431,432comprises identical teeth4311,4321. The circumferential orientation of the two adjoining sprockets431,432differs by half a pitch P, i.e. one tooth4311of the first sprocket431is circumferentially offset to one tooth4321of the second sprocket432by half a pitch. In this embodiment, two identical chain wheels, comprising identical sprockets431,432and identical anti-twist devices434are being used. In this embodiment, the anti-twist device comprises individual fitting keys for each of the sprockets. Other embodiments with aligned cavities for inserting a common fitting key or other shaft to collar connections are also possible that ensure a solid rotational connection. The spacer435provides a means to adjust the axial distance between the first and the second sprocket.

In this embodiment, the spacer435together with a shaft part437of the second sprocket432form an intermediate space438adapted to receive the damping elements.

As shown inFIG. 7, the pitch P of a sprocket is defined as the circumferential distance between two adjoining teeth4311,4321.

FIGS. 8 to 11show the first embodiment of a damping element according to the invention in detail. However, the fixations61,62on either free end of the damping element are similar or identical to the ones of the other embodiments. In essence, the damping element6is of a folded sheet metal design with a first fixation61on its one free end for the lateral fixation to the first chain51, a second fixation62on its opposite free end for the lateral fixation to the second chain52and a force transmission unit63being arranged between the first and the second fixation transmitting an applied force from the first fixation61to the second fixation62and vice versa.

The first fixation61in this embodiment is a clip with two opposing clamping jaws611for clamping an outer link plate512of the first chain51between the two rollers514being supported by said outer link plate512and between the two adjoining inner link plates511on either side of said outer link plate512. At the free end of each of the clamping jaws611, hooks612are being formed to better clench said outer link plate512. For a better application, the hooks612are tapered and narrow towards their extremities. As can be seen inFIG. 10, the hooks612are realized by bending the end tip of the clamping jaws611by a hook angle α of more than 90 degrees in the direction of the opposite clamping jaw.

From the part of the first clip61connecting the two adjoining clamping jaws611the clamping jaws611extend in essence perpendicular to said connecting part. A first flap64extends inclined from said part in the same direction from said part as the clamping jaws611extend from said part, forming a flap angle β. Said flap angel, in the current embodiment is around 60 degrees, however, other, smaller or larger angles are possible.

The second fixation62is of identical design and the force transmission unit63in this embodiment is a leaf spring, in particular an arc-shaped leaf spring comprising a short arm631, a long arm632and an arc633arranged in between these arms. In the depicted embodiment, the length of the short arm631and the long arm632differs by half a pitch. In other embodiments, said length differs by (2*n+1) times half a pitch, wherein n is an integer.

In order to realise a pretension between the first and the second chain, the arc-shaped leaf spring63is bent by a pretension angle γ of less than 180 degrees. When the damping element6is positioned between the two adjoining chains, the two free ends of the damping element are pressed together resulting in an outward directed clamping force.

In order to produce a damping element6as described above, a flat projection of the damping element body can be cut out of a steel sheet, representing a base plane. The clamping jaws and the adjoining flap forming a cross-like shape on either free end of said cut out body. In one step, the clamping jaws are bent in essence perpendicular to the base plane. In another step, the tips of the clamping jaws are bent inwards towards each other by a hook angle α of more than 90 degrees, in particular by 120 degrees. In another step, the flaps are bent towards the same direction as the clamping jaws by a flap angle β of around 60 degrees. The above described steps can be performed at the same time on both free ends of the damping element. In a last step, the middle section of the flat projection is bent by a pretension angle γ of less than 180 degrees, as such that the clamping jaws together with the flaps are oriented towards the outside.

FIG. 12shows a third embodiment of a damping element6b. In essence, the attachment of the damping element to the respective chain is identical to the first embodiment, i.e. the clamping jaws and the flaps. Instead of an arc-shaped leaf spring63connecting the first and the second connection, a magnet unit8is present. In use, the magnets83can be in contact with each other or they can be spaced apart from one another.

The magnet unit8comprises magnet holders82and magnets83. The magnet holders82can be formed integrally as a single piece together with the clamping jaws and the flaps or can be attached to them. The magnets83are attached to the magnet holders82or can be directly attached to the clamping jaws and flaps. In the depicted embodiment, the first fixation61together with a first magnet holder82and a first magnet83are identical to the second fixation62together with a second magnet holder82and a second magnet83.

FIG. 13shows a fourth embodiment of a damping element6c. Like the third embodiment6b, the clamping jaws and the flaps are identical to the ones of the first embodiment. In order to transmit forces from the first fixation61to a second fixation62, a tension or pressure spring unit9is present.

The tension or pressure spring unit9comprises spring holders92and springs93. A single spring or a plurality of springs can be present. The spring holders92can be formed integrally as a single piece together with the clamping jaws and the flaps or can be attached to them. The springs93are attached to the spring holders92or can be directly attached to the clamping jaws and flaps. In the depicted embodiment, the first fixation61together with a first spring holder92are identical to the second fixation62together with a second spring holder92.

FIGS. 14 and 15show a fourth embodiment of a damping element80. The damping element80comprises an integrally formed housing800, being T-shaped in essence. In the view ofFIG. 14, in the use situation, the housing looks like a lying T. The housing800comprising a first leg, forming the first fixation801, is oriented parallel to the first chain51in the use situation. A second leg, forming the second fixation802, is oriented perpendicular to the first leg and arranged in the middle thereof, extending in the direction of the second chain52in the use situation. On the first fixation801, in the direction that is opposite of the second fixation802, a first pin reception8013is present on either free end of the first leg facing laterally towards the first chain.

The first pin reception8013comprises a cylindrical shape and its diameter is slightly bigger than the pin513of the chain51to be received, providing some clearance between the respective pin and the corresponding side wall of the first pin reception8013. The distance between these two first pin receptions8013matches the pitch of the first chain51.

Adjoining to the first pin reception8013and collinear with its rotational axle, a first magnet reception8011is formed in the first leg and is adapted to receive a magnet803, that can be inserted from the side opposite to the first pin reception8013. The first magnet reception8011, in essence, comprises a cylindrical shape that widens conically from a base diameter, arranged adjacent to the first pin reception8013, towards the direction opposite to the first pin reception8013. The base diameter matches the diameter of a magnet to be inserted towards. The difference in diameter of the first pin reception8013and the first magnet reception8011forms a first shoulder8012, on which the corresponding magnet803abuts.

In the middle of the two first pin receptions8013, in the direction of the second leg, a second magnet reception8021is formed and a second pin reception8023is formed adjacent and collinear thereto. The shape and design of the second magnet reception8021and the second pin reception8013are in essence equal to the first magnet reception8011respective the first pin reception8013, being oriented towards the opposite direction. The difference in diameter of the second pin reception8023and the second magnet reception8021forms a second shoulder8022, on which the corresponding magnet803abuts.

In this embodiment, the second fixation802comprises only one second pin reception8013. However, other embodiments with more than one second pin reception are possible, resulting in a damping element, whose shape differs from the T-shape.