GB2108616A

GB2108616A - Belt tensioning device

Info

Publication number: GB2108616A
Application number: GB08230789A
Authority: GB
Inventors: H Reinhard Smetz
Original assignee: RUD Kettenfabrik Rieger und Dietz GmbH and Co KG
Current assignee: RUD Kettenfabrik Rieger und Dietz GmbH and Co KG
Priority date: 1981-11-06
Filing date: 1982-10-28
Publication date: 1983-05-18
Also published as: CH658823A5; SE8206122L; SE456974B; ATA395082A; BE894873A; BR8206432A; SE8206122D0; GB2108616B; AT390489B; NL8204267A

Abstract

In a tensioning device for tensioning a belt (16), the connection element (15) for the belt (16) is mounted on a connection part (1) so as to be displaceable against the effect of at least one spring (22). When the connection element (15) is displaced against the force of the spring (22), an indication is given and/or the tensioning force exerted on the belt (16) is limited. <IMAGE>

Description

SPECIFICATION Tensioning device The invention relates to a tensioning device for tensioning lines, especially belts, with a connection part having a connection element, with a drive part mounted pivotably on the connection part, with a drive element rotatable about its pivot axis, with at least one ratchet wheel connected fixed against rotation to the drive element, with a detent pawl arranged displaceably on the.

connection part and engaging resiliently with the ratchet wheel, and with a drive pawl arranged displaceably on the drive part and engaging resiliently with the ratchet wheel, in which tensioning device, during the movement of the drive part in one direction, the latter rotates the drive element via the drive pawl and the ratchet wheel, and during movement in the other direction the drive element is retained by the detent pawl.

Tensioning devices of the type mentioned above are known, for example, from German Offenlegungsschrift 2,916,902; they are also referred to, in practice, as clamping ratchets. The known tensioning devices are not entirely satisfactory in as much as they do not give their user any indication as to the amount of the tensioning forces loading the tensioning lines.

Now it would be possible, of course, to incorporate a force indicator device in a tensioning arrangement, as it were connected in series with the tensioning device. However, the arrangement would become considerably more difficult to handle as a result.

The object on which the invention is based is to provide a tensioning device of the type in question, which indicates the tensioning force to the user and/or automatically prevents the tensioning lines from being overloaded.

This object is achieved, according to the invention, due to the fact that the tensioning device is provided with means for indicating the tensioning force and/or for limiting the tensioning force, these means incorporating a spring, against the effect of which the connection element is mounted on the connection part so as to be movable to and fro.

It is especially advantageous if the tensioning device has at least one control element which serves for controlling at least one locking element, by means of which the ratchet wheel is stopped so as to prevent a specific spring force from being exceeded. The advantage of this solution may be seen in the fact that, in it, the tensioning operation is interrupted automatically when a predetermined tensioning force is reached.

A second advantageous solution is one in which the tensioning device has a control element which serves for controlling an acoustic signal transmitter which indicates that a specific spring force has been reached. In this case, it is possible for the user to vary the maximum tensioning force within limits, that is to say to adapt it to the material and design of the particular tensioning line, and by a combination of the two solutions, on the one hand, it is possible to indicate acoustically that a tensioning-force range which can be viewed as sufficient has been entered and, on the other hand, automatic maximum force limitation can be provided.

Further details and features of the invention emerge from the claims and from the description of several exemplary embodiments illustrated in the attached drawing in which: Figure 1 shows a section through a first tensioning device; Figure 2 shows, partially in cross-section, a plan view of the tensioning device according to Figure 1; Figure 3 shows a detail of the tensioning device according to Figures 1 and 2; Figure 4 shows a section through a second tensioning device; Figure 5 shows, partially in cross-section, a plan view of the tensioning device according to Figure 4; Figure 6 shows a detail of the tensioning device according to Figures 4 and 5; Figure 7 shows a detail of the tensioning device according to Figures 4 to 6 in a first position; Figure 8 shows a detail of the tensioning device according to Figures 4 to 6 in a second position;; Figure 9 shows a section through a third tensioning device; Figure 10 shows, partially in cross-section, a plan view of the tensioning device according to Figure 9; 'Figure 11 shows a detail of the tensioning device according to Figures 9 and 10 in a first operating position; Figure 12 shows a detail of the tensioning device according to Figures 9 and 10 in a second operating position; and Figure 13 shows a detail of the tensioning device according to Figures 9 and 10 in a third operating position; Figure 14 shows a section through a further tensioning device; Figure 1 5 shows a plan view of the tensioning device according to Figure 14; Figure 1 6 shows a partial view, corresponding to Figure 14, of a modified tensioning device; and Figure 1 7 shows a detail of a tensioning device working with an acoustic signal transmitter.

Substantially the same reference numerals are used in the Figures for parts corresponding to one another.

The tensioning device illustrated in Figures 1 and 2 possesses a connection part designated as a whole by 1 and a drive part designated as a whole by 2. The connection part 1 and thedrive part 2 are connected to one another via a drive element 3 which, when the tensioning device is designed for tensioning belts, as in the exemplary embodiment illustrated, is provided with an insertion slit 4 for receiving a belt end (not shown).

Located in the region of the ends of the drive element 3 are ratchet wheels 5 connected fixed against rotation to the latter. In practice, the drive element 3 is formed by two semi-circular bolts which have the cross-sections visible in Figure 1 and which are held together by the ratchet wheels 5 having orifices corresponding to the crosssections shown. Assigned to the ratchet wheels 5 are a drive pawl 6 mounted resiliently on the drive part 2 and a detent pawl 7 likewise mounted resiliently on the connection part 1. When the drive part 2 pivots, the drive pawl 6 engages by means of projections 8 behind teeth 9 of the ratchet wheels 5 and carries with it via the ratchet wheels 5 the drive element 3 which thereby rotates in the direction of the arrow 10 in Figure 1.

Backward rotation of the drive element under the tensile force of the tensioning line is prevented by projections 11, likewise interacting with the teeth 9 of the ratchet wheel 5, of the detent pawl 7 which is under the effect of a compression spring 12. During the return movement of the drive part 2 counter to the direction of the arrow 10, the drive pawl 6 is lifted over the teeth 9 of the ratchet wheels 5 against the effect of a spring (not shown).

At the end of the connection part 1 facing away from the pivot axis for the drive part 2, a carriage 14 is guided between raised cheeks 13 of the connection part. This carriage carries a connection element 1 5 for the end loop of a belt 1 6. The connection element 1 5 is formed by a retaining bolt which is provided at one end with a threaded portion 1 9 which is separated from a main part 1 8 by an annular groove 1 7 and which can be screwed through a threaded bore 20, the thread of which is located in the region of the annular groove 1 7 in the desired position of the connection element 15, as shown in Figure 2.The connection-element is mounted with play in guide bores 21 in the cheeks, the axes of which are aligned with the axis of the threaded bore 20. The play of the connection element in the guide bores 21 is made so great, here, that the axis of the threaded portion 19 screwed through the threaded bore 20 is offset relative to the axis of the threaded bore 20 by an amount which prevents the threaded portion 19 from being unscrewed when the connection element is loaded.

The carriage 14 is supported against a yoke 23 of the connection part via two springs 22 which are formed by sets of cup springs and which are deformed as a function of the tensioning force. In the central region of the carriage 14, a control element 26 is mounted in guide bores 24 and 25.

The control element 26 carries a stop 27 which is formed by two lock nuts and which is pressed by a deflecting spring 28 against a wall portion of the carriage 14. So that the position of the control element 26 can be adjusted, the latter is provided at one end with a line marking 29.

Transversely to the longitudinal axis of the connection part 1, a locking element 32 which is under the effect of an actuating spring 31 is mounted on a bolt 30.

Figure 3 shows a detail of the tensioning device according to Figures 1 and 2. It indicates a slit 33 which is fashioned in the side cheeks 13 and the shape of which is selected so that the yoke 23 can be introduced directly into its desired position.

Located on the outside of the cheek 1 3 is a marking 34 which allows the user of the tensioning device, under favourable light conditions, to ascertain the amount of compression of the springs 22 from outside, specifically by means of a projection 35 of the carriage 14.

When, during use of the tensioning device described, a force is exerted on the connection element 1 5 by the belt 16, the carriage 14 endeavours to move to the right against the effect of the springs 22 in Figures 1 and 2. In so doing, it carries the control element 26 with it over the stop 27. After a specific force has been reached, the left-hand end of the control element 26 releases the end face of the locking element 32, and the latter is transferred downwards into the position shown by dot-and-dash lines under the effect of the actuating spring 31 in Figure 2, specifically at a moment when the detent pawl 7 engages into the gap between successive teeth 9 of the ratchet wheel 5.Since the locking element 32 rests, in the locking position, against the end face of the projection 36 of the detent pawl, the latter cannot move out of the tooth gap again, that is to say the ratchet wheels are stopped automatically when a specific tensioning force is reached.

So that the tension can be cancelled again, the drive pawl 6 must be removed from the region of the teeth 9 of the ratchet wheels 5 by hand against the effect of a spring. After that, the drive part can pivot further in an anti-clockwise direction, as shown in Figure 1, beyond a stop 37.

The result is that a control cam 38 connected to the drive part 2 presses against the end of the detent pawl 7 facing it and seeks to push the latter against the effect of the compression spring 12 to the right, as seen in Figures 1 and 2. So that the detent pawl 7 can actually be released, the locking element 32 must first be returned into its initial position by hand against the effect of the actuating spring 31.

Figures 4 to 8 show a tensioning device with a locking element 40 which is mounted on a transverse slide 39 and which does not have to be moved back into its inactive position by hand, as in the case previously described, but can be removed from its locking position as a result of pivoting of the drive part 2 and by means of an unlocking pawl 41. The same control cam 38 also used to actuate the detent pawl 7 serves for actuating the unlocking pawl 41. It goes without saying that, even in this case, before unlocking, the drive pawl 6 has to be removed not only from the region of the teeth of the ratchet wheels 5, but also from the region of the stop 37. Subsequently, it can be rotated further in an anti-clockwise direction by an amount limited by an end stop 42, and the control cam 38 acts successively first on the unlocking pawl 41 and subsequently on the detent pawl 7.

The transverse slide 39 is mounted in a connection part 1 so as to be movable to and fro.

Compression springs 43 hold it in the position shown in Figure 5. To transfer the locking element 40 from the position shown by solid lines in Figure 5, in which it allows movements of the detent paw 7, into the position indicated by dotand-dash lines, in which movements of the detent pawl 7 are no longer possible, the transverse slide 39 must be moved downwards, as seen in Figure 5. There serves for carrying out this movement a control element 44 which is designed as an engagement device and one end of which surrounds a bush 45 which, together with a bush 46, assumes a function of the carriage 14 in the exemplary embodiment according to Figures 1 and 2. When the springs 22 are compressed during tensioning of the belt 1 6, the control element 44 in Figure 5 moves to the right.The result is that a projection 47 of the control element 44 presses against the control slope 48 of the transverse slide 39 and transfers the latter into the position indicated by dot-and-dash lines.

Together with the transverse slide 39, the locking element 40 is moved downwards.

The possibility cannot be excluded that the tensioning force initiating the locking operation occurs at a moment when the projection 36 of the detent pawl 7 is located in the path of movement of the locking element 40. In such a case, the compression spring 43 assumes the function of a deflecting spring, that is to say it allows the locking element to move back briefly, and the latter passes into an end position defined by a stop 49 only as soon as the projection 36 has moved back to the left, as seen in Figure 5. In this end position, the locking element projects into the region of the end face of the projection 36 and holds the detent pawl 7 in the tooth gap previously occupied.

Figures 7 and 8 which show the locking element 40 from below serve for a better understanding of the interaction between the detent pawl 7 and the unlocking pawl 41. Figure 7 shows the situation of the locking element 40 in its inactive position, whilst Figure 8 represents the locking position of the locking element 40. Whilst 36 denotes the projection of the detent pawl 7, 50 denotes a projection of the unlocking pawl 41. As may be seen in Figures 7 and 8, the projection 50 and the locking element 40 are provided with control slopes 51 and 52. When a pressure is exerted on the end of the unlocking pawl 41, on the left in Figure 4, by means of the control cam 38, the control slopes 51 and 52 are brought to rest against one another.The result is that via the pair of control slopes 51 and 52 the locking element 40 is moved, as seen in Figure 8, downwards against the effect of the compression spring 43, that is to say out of the locking position for the projection 36 of the detent pawl 7.

An adjusting screw 53 serves for determining the locking position for the locking element 40.

An especially advantageous solution is illustrated in Figures 10 to 13. This involves automatic positive unlocking when the belt tension ceases. The user of the tensioning device can therefore attempt, at specific intervals of time, to move the drive part 2 again. If the belt tension has not fallen, a movement of the drive part 2 is not possible, as in the constructions described hitherto. If, on the other hand, the belt tension has fallen by a specific amount, retensioning can be carried out. The possibility of retensioning signals to the user of the tensioning device, in other words, settling of the load or creeping of belts which may be used.

So that positive unlocking can be carried out, the carriage 14 is provided with a projection 54 which is arranged parallel to the control element 26 and which, like the control element 26, projects, when the tensioning device is not loaded, into the path of movement of a locking element 56 mounted on a bar 55.

Figure 11 shows the locking element 56 from below when the tensioning device is in the unloaded state. In this position, it is pressed by means of an end face against a projection 54.

When a sufficiently great force is exerted on the connection element 15, the carriage 1 4 moves to the right under the compression of the springs 22, specifically into the position shown in Figure 12, in which a distance X0 is obtained between the associated stop surfaces 57 and 58 of the connection part 1 and of the carriage 14. In this position, the locking element 56 is moved upwards, as seen in Figure 12, under the effect of the actuating spring 31, since its end face turned towards the control element 26 is released from this. A to-and-fro movement of the detent pawl 7 or its projection 36 is no longer possible. When the tensioning force ceases, the carriage 14 is moved to the left again by the springs 22.The result is that the projection 54 is pressed against a control slope 59 of the locking element 56, and because of an appropriately selected angle of incidence of the control slope 59 the locking element 56 is pressed downwards against the effect of the actuating spring 31, specifically until it is moved out of the region of the end face of the projection 36. This means, however, that the detent pawl is unlocked, and new tensioning can take place by means of the drive part 2.

Figures 14 to 1 6 show two further tensioning devices which differ only slightly from one another, and specifically the lower part of Figure 1 5 and Figure 14 belong together and the upper part of Figure 1 5 and Figure 1 6 belong together.

In the tensioning devices according to Figures 14 to 16, a locking element 60 formed by a pawl is used. The pawl 60 is mounted fixed against rotation on a shaft in the connection part 1.

Assigned to the locking element 60 are additional ratchet wheels 61 which are connected fixed against rotation to the ratchet wheels 5 for driving the drive element 3 and teeth 62 of which are oriented in an opposite direction to the teeth of the first ratchet wheels. Used as control elements 63 and 64 are connecting rods, one end of which is connected to the locking elements 60 and the other end of which is supported via a deflecting spring 65 against stop surfaces formed by the carriage 14. Whereas, in the exemplary embodiment illustrated in the upper part of Figure 1 5 and in Figure 16, the control element 63 is located outside the connection part 1, in the embodiment illustrated in the lower part of Figure 15 and in Figure 14 the control element 64 is located inside the connection part 1 and is therefore protected against external influences.

The position of the control elements 64 and 65 can be varied by means of adjusting stops 66. To ensure that when the spring 22 is relaxed the locking element 60 is transferred back into the release position from the locking position, the control elements 63 and 64 are provided with additional stops 67, against which the end face of the carriage 14 presses as soon as the carriage 14 moves to the left in Figures 14 and 15.

The mounting of the connection element 1 5 in the last-mentioned exemplary embodiment has proved especially successful. As may be seen in Figure 1 5, the end 68 of the leg 69 of the carriage is bent round several times and not only provides the threaded bore 20, but also protects the threaded portion 1 9 against attacks and damage from outside.

Figure 1 7 indicates how, by means of a slight modification of the tensioning device according to Figures 14 and 15, it is possible to reach a solution with a control element 70 which is formed, like the control elements 63 and 64, by a control rod and which serves for controlling an acoustic signal transmitter 71 formed by a spring and located on a pivoting lever 72 mounted on the connection part 1 in the same way as the locking elements 60. As soon as the signal transmitter enters the region of a ratchet wheel 73, the signal transmitter 71 strikes against the teeth 74 of the ratchet wheel, and there arises an easily perceptible noise which must, of course, differ sufficiently clearly from the noise originating from the ratchet.

The tensioning devices described are all based on the notion of mounting the connection element 15, also designated as a fixed end, of the tensioning device on the connection part so as to be displaceable against the force of the spring, thereby to obtain a distance indicator which either prevents further tensioning via a control element when a specific spring force is reached or requests the user of the tensioning device to terminate the tensioning operation in response to a visual indication or the transmission of an acoustic signal. The advantages of the tensioning devices illustrated and described, which all consist of parts which can be assembled simply and easily, are considerable, because as a result of the indicator and locking mechanisms integrated in the tensioning devices undesirable overloading of the tensioning lines can be reliably prevented.

Claims

1. A tensioning device for tensioning lines, especially belts, comprising a connection part having a connection element, a drive part pivotably mounted on the connection part, a drive element rotatable about the pivot axis of the drive part with at least one ratchet wheel connected fixed against rotation to the drive element, a detent pawl arranged displaceably on the connection part and engaging resiliently with the ratchet wheel, and a drive pawl arranged displaceably on the drive part and engaging resiliently with the ratchet wheel, the construction being such that, during the movement of the drive part in one direction, the latter rotates the drive element via the drive pawl and the ratchet wheel and, during movement in the other direction, the drive element is retained by the detent pawl, in which means are provided for indicating the tensioning force and/or for limiting the tensioning force, these means ir,lcorporating a spring against the effect of which the connection element is mounted on the connection part so as to be movable to and fro.

2. A tensioning device according to claim 1 having at least one control element which serves to control at least one locking element by means of which the ratchet wheel is stopped so as to prevent a specific spring force from being exceeded.

3. A tensioning device according to claim 1 or claim 2 having a control element which serves to control an acoustic signal transmitter which indicates that a specific spring force has been reached.

4. A tensioning device according to claim 2, in which the locking element is formed by a pawl which is mounted pivotably on the connection part and to which is assigned an additional ratchet wheel which is connected fixed against rotation to the ratchet wheel for driving the drive element and the teeth of which are orientated in an opposite direction to the teeth of the first ratchet wheel.

5. A tensioning device according to claim 4, in which the control element is formed by a control rod one end of which is connected to the locking element and the other end of which is supported via a deflecting spring against a stop surface which is disposed on a carriage, movable to and fro, mounted on the connection part and carrying the connection element.

6. A tensioning device according to claim 3, in which the acoustic signal transmitter is formed by a tongue which is located on a pivoting lever mounted pivotably on the connection part and which generates noises when it strikes on the teeth of a ratchet wheel.

7. A tensioning device according to claim 2, in which the locking element is formed by a slide mounted so as to be movable transversely to the longitudinal axis of the connection part.

8. A tensioning device according to claim 2 or claim 7, in which, when released by the control element, the locking element can be transferred by means of an actuating spring from an inactive position into the stopping position.

9. A tensioning device according to any one of claims 2, 7 or 8, in which, in the stopping position, the locking element keeps the detent pawl engaged with the teeth of the ratchet wheel for driving the drive element.

1 0. A tensioning device according to any one of claims 2, 7, 8 or 9, in which the control element is located on a carriage which carries the connection element and is mounted on the connection part and which is supported against a yoke of the connection part via the spring deformed as a function of the tensioning force.

11. A tensioning device according to any one of claims 2, 7, 8, 9 or 10, in which the control element is adjustable.

12. A tensioning device according to any one of claims 2, 7, 8, 9, 10 or 11, in which the locking element is formed by a bush which is mounted on a bolt and can be transferred into its release position by hand.

1 3. A tensioning device according to any one of claims 2, 7, 8, 9, 10 or 11, in which an unlocking pawl mounted on the connection part serves for transferring the locking element from the locking position into its release position.

1 4. A tensioning device according to claim 13, in which a control cam connected to the drive part serves for actuating the unlocking pawl.

1 5. A tensioning device according to claim 1 3 or claim 14, in which the unlocking pawl is provided with a projection which has a control slope for displacing the locking element.

1 6. A tensioning device according to any one of claims 13 to 15, in which the locking element is mounted fixed against rotation on a cross bar of the connection part.

1 7. A tensioning device according to claim 2 or any claim appendant thereto, in which, when the tensioning force drops to a specific value, the locking element can be transferred back into its release position by means of a projection located on the carriage under the effect of the force of the spring deformed as a function of the tensioning force.

1 8. A tensioning device according to claim 2 or any claim appendant thereto, in which the control element is mounted on the carriage so as to be movable against the force of a deflecting spring.

1 9. A tensioning device according to any preceding claim, in which the connection element is formed by a retaining bolt which is provided at one end with a threaded portion which is separated from its main part by an annular groove and which can be screwed through a threaded bore the thread of which is located in the region of the annular groove in the desired position of the connection element.

20. A tensioning device according to claim 19, in which the connection element is mounted with play in guide bores the axes of which are aligned with the axis of the threaded bore.

21. A tensioning device according to claim 20, in which the play of the connection element in the guide bore is so great that the axis of the threaded portion screwed through the threaded bore is offset relatively to the axis of the threaded bore by an amount which prevents the threaded portion from being unscrewed when the connection element is loaded.

22. A tensioning device according to any one of claims 1 to 20, in which each spring deformed as a function of the tensioning force is located between parallel cheeks of the connection part.

23. A tensioning device according to claim 22, in which each spring deformed as a function of the tensioning force is mounted on pins of a yoke which is retained in slits in the cheeks of the connection part and which engages through slits in legs of a carriage carrying the connection element.

24. A tensioning device according to any one of claims 19 to 21, in which the connection element is mounted in guide bores which are located in legs of an essentially shackle-shaped carriage.

25. A tensioning device according to claim 24, in which one of the legs of the carriage has at least one simple bent-round end in which is fashioned the threaded bore for the threaded portion of the connection element.

26. A tensioning device according to claim 25, in which the threaded portion is covered by the bent-round end of one leg of the carriage.

27. A tensioning device according to any preceding claim, in which the connection part is provided with cheeks which have slots for guiding the connection element or a carriage carrying the latter.

28. A tensioning device according to any preceding claim, in which at least one control cam is provided which is connected to the drive part and by means of which, when the drive pawl is removed from the ratchet region of the ratchet wheel the detent pawl, can likewise be removed from the region of the ratchet wheel.

29. A tensioning device according to any preceding claim having two cup-spring assemblies each forming a spring deformed as a function of the tensioning force.

30. A tensioning device substantially as described herein with reference to the accompanying drawings.