Tensioning and damping element for endless chain drive, especially for roller chain drives

Abstract

A tensioning and damping element for endless chain drives, especially for roller chain drives, can be used for endless chain drives, which are to be tensioned diametrically. The material is an elastic plastic. All told, the known tensioning and damping elements, in conjunction with the wear of the chain, the load changing phases, as well as the reversing according to the degree of deformation, have the disadvantage of a phased running irregularity, an increased running noise and of wear-intensive areas in the toothed rim. An element with a ring part and a toothed rim of arc-shaped teeth with, in each case, axially opposite bulges in the roller-seating and, between these, roller-seating depressions, grooves, which are disposed peripherally between the ring part and the bulges, an extended pitch and extended roller-seatings with the advantageous profile shape similar to a semielliptical curve lying on the root circle.

Claims

1. A tensioning and damping element, wherein the tensioning and damping element is disposable between a tight side and a slack side of an endless chain drive and thereby acting constantly on both sides of the endless chain drive, the tensioning and damping element being formed as an elastically deformable element which includes elastic plastic, and comprising: a ring part, at the outer periphery of the ring part, a corresponding toothed rim, capable of gripping the endless chain drive, elastically deformable, laterally open teeth and, in a root circle of the toothed rim, radially elastic roller-seatings between the teeth, which pass into the ring part, and wherein the tensioning and damping element is deformable between a shape of a concentric element and a shape of a Cassinian curve with a shape close to an ellipse, the diameter of a pitch circle or a smallest axis of the tensioning and damping element being larger than a diameter of a pitch circle of a smallest chain sprocket of the endless chain drive, wherein the radially elastic roller-seatings have bulges, which are axially on opposite sides in the width of the radially elastic roller-seatings, arranged on either side of the ring part and lying externally on a root circle with a roller-seating depression of a depth e.sub.0=0.5(D.sub.fD.sub.v), D.sub.f being the diameter of the root circle and D.sub.v being the diameter of a depression circle, the roller-seating depression extends centrally between the bulges in the ring part between the root circle and the depression circle, the amount e.sub.0 of which, in a stress-free starting position, is larger than the amount of a height h.sub.1 in a camber in an elliptical, pretensioned state, wherein the toothed rim has grooves between the ring part and the bulges, and wherein the toothed rim has an extended pitch q.sub.0 with 1.02p.sub.0<q.sub.0<1.08p.sub.0, p.sub.0 being a pitch of the endless roller chain, which is not worn out, wherein the radially elastic roller-seatings are extended with a profile shape similar to a semi-elliptical curve, which lies radially on the root circle and which has a main apex axis between two points which, projected on the pitch circle, has a length l.sub.0, which is given by 1.1d.sub.1<l.sub.0<1.45d.sub.1, wherein d.sub.1 is a diameter of a roller of the endless roller chain.

2. The tensioning and damping element of claim 1, wherein the extended pitch is q.sub.0=1.05p.sub.0.

3. The tensioning and damping element of claim 1, wherein the length is l.sub.0=1.25d.sub.1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows the image of a tensioning and damping element as a finished product.

(2) FIG. 2 shows the engagement picture of the tensioning and damping element for the respective end positions of the stress-free concentric shape and the pre-stressed elliptical shape

(3) FIG. 3 shows a cutout from the engagement picture of the tensioning and damping element for the end position of the elliptical shape with a chain, which is not worn out.

(4) FIG. 4 shows a cutout from the engagement picture of the tensioning and damping element for the end position of the concentric shape when the chain is elongated due to wear.

(5) FIG. 5 shows a sectional representation through a roller-seating in the stress-free state.

(6) FIG. 6 shows a sectional representation through a roller-seating in the case of an elliptical deformation.

(7) FIG. 7 shows the projection of the contact zones of the roller-seatings of the concentric tensioning and damping element to the chain rollers.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

(8) The tensioning and damping element, shown in FIG. 1, is concentric. In this not pretensioned configuration, it corresponds to the configuration of the finished product.

(9) As is evident from FIGS. 1 and 2, as well as FIGS. 5 and 7, the tensioning and damping element has, on the inside of the root circle, a ring part 4, which is partly exposed under the teeth 1 of the toothed rim and blends over its circumferential surface 2 with the roller-seatings 3 of the toothed rim in the root circle D.sub.f.

(10) The roller-seatings of the tooth profile have bulges 5a, 5b, which, in profile, are disposed opposite to one another and extend into the tooth flanks and into the root circle D.sub.f. Centrally between the bulges and extending in the ring part up to the depression circle D.sub.v, there are roller-seating depressions 6 with a depth of e.sub.0=0.5(D.sub.fD.sub.v).

(11) The bulges are free-standing on the planar side and on the outside and form grooves 7a, 7b to the ring part.

(12) As shown in FIG. 7, the contact regions between the roller-seatings and the rollers of the chain are resting on the bulges. The roller-seating depressions are exposed to the roller-seatings.

(13) Any undesirable transfer of heat from the bulges into the ring part is interrupted by the grooves.

(14) If, as shown in FIG. 2, elliptical deformation of the tensioning and damping element leads to pressure deformation of the roller-seating, the latter, as shown in FIG. 6, is compressed in the region of the root circle in such a manner, that a camber 8, with a height h1 is formed and the roller-seating depression becomes smaller. On the condition that the height of the camber h.sub.1<e.sub.0, there are stable roller supports on either side on the bulges of the roller seating. Owing to the fact that the bulges extend up into the flanks of the teeth, the chain engagement, from the initial up to the loosening contact, is assured with stable support in the roller seating for all deformation conditions between the end positions.

(15) As is furthermore evident from FIG. 2, there is, for the end positions of the stress-free concentric shape and the pre-stressed elliptical shape, no agreement between the pitch q.sub.0 of the concentric shape corresponding at the same time to the finished part and the pitch q.sub.1 of the toothed rim corresponding to the pre-tensioned elliptical shape. Moreover, q.sub.0>q.sub.1.

(16) Likewise, there is no agreement between the pitches p.sub.a and p.sub.1 of the chain.

(17) The pitch of the tensioning and damping element, which determines the dimensions and manufacture, is the pitch p.sub.a of the chain 9a, which is not worn out at the beginning of the operating time. On the other hand, the pitch p.sub.1 is that of the worn-out chain 9b with p.sub.1>p.sub.0.

(18) For a precise engagement of the chain, the pitch q.sub.1 of the tensioning and damping element is specified by q.sub.1p.sub.0, the closing movement of the toothed rim and the condition that there should be no jamming of the chain rollers having been taken into consideration. As the chain becomes worn out, the original pitch of the chain increases until the elongation due to wear reaches the dimension p.sub.1 and the degree of deformation of the tensioning and damping element reaches the concentric shape with the pitch q.sub.0.

(19) At the end of the operating period, the chain, shown by way of example, has an elongation due to wear of 3%, so that a pitch of p.sub.1=1.03p.sub.0 results. For this elongation of the worn-out chain 9b, the tensioning and damping element is concentric and no longer pretensioned at the end of its tensioning path.

(20) Owing to the fact that the toothed rim lies outside of the neutral bending line 10 of the ring part, the pitch of the concentric shape q.sub.0 is larger than the pitch of the elliptical shape q.sub.1 with regard to the engagement region of the tensioning and damping element to the chain.

(21) The disadvantageous compression of the toothed rim in the contact region to the chain accordingly is prevented in that the pitch q.sub.0 of the toothed rim is enlarged to such an extent that, in each phase of the deformation, it is larger than the amount of the chain pitch with the pitch p.sub.1.

(22) For this extended pitch q.sub.0, q.sub.0=1.05p.sub.0 was determined to be particularly suitable.

(23) With this extension of the pitch, there is an improved correspondence of the pitch of the roller-seatings of the toothed rim between the dimension-determining chain contact of the engaging chain roller and the incipient contacting and contact loosening chain rollers over the whole operating period.

(24) As it is evident from FIG. 3, the toothed rim of the tensioning and damping element, at the beginning of the operating period with a chain that is not worn, engages the chain in the end position of the elliptical shape in the smaller curvature characteristic of the secondary crown area. Moreover, the tooth profile is compressed and forms an adjacent roller-seating 3 to the engaging roller 11. The distance to the respective upstream and downstream roller seating is q.sub.1. For the explanation, given by way of example, p.sub.0=q.sub.1 was selected. The rollers of the chain links of the new chain, upstream and downstream from the dimension determining engagement, accordingly intervene in the pitch agreement.

(25) As is evident from FIG. 4, when the chain is elongated due to wear and at the end of the tensioning path s, the toothed rim of the tensioning and damping element engages the end position of the concentric shape in the radial curvature characteristic of the circular segment. At the same time, the radial curvature corresponds to the curvature of the finished part. In accordance with the manufacture, the toothed rim has a pitch q.sub.0 and an extended pitch circle, corresponding to the number of teeth.

(26) In deviation from the usual tooth profile for chain sprockets with radial roller-seatings, the tooth profile has regularly extended roller-seatings 3. The roller-seatings, resting on the root circle, have a profile shape similar to a semi-elliptical curve. The main apex axis between the points W.sub.1 and W.sub.2 and projected on the pitch circle D.sub.o, has a length of l.sub.0. The depth of the roller-seatings arises from the elliptical ratio. The heights of the teeth lie within the tip circle. With the depressions of the roller-seating hollows, the roller seatings rest tangentially on the root circle of the tensioning and damping element and extend up into the tooth flanks.

(27) For the length l.sub.0 of the main apex axis of the profile shape between the points W.sub.1 and W.sub.2, a factor of l.sub.0=1.25d.sub.1 was used, by way of example, with regard to the roller diameter d.sub.1 of the chain.

(28) With that, the tensioning and damping element with the extended roller-seatings, independently of its deformation and of the state of wear of the chain, contacts the rollers of the chain, which they are constantly capable of gripping, between the dimension determining engaging chain roller and the incipiently contacting and contact loosening chain rollers with an increased pitch and shape tolerance over the whole operating period with the result of improved running, less running noise and less wear. Moreover, it can be used in an area with longer tensioning paths and higher chain speeds.