EP0408621A1

EP0408621A1 - Strap tightening device

Info

Publication number: EP0408621A1
Application number: EP19890903824
Authority: EP
Inventors: Lennart Lindblad
Original assignee: Linvent AB
Current assignee: Linvent AB
Priority date: 1988-03-18
Filing date: 1989-03-17
Publication date: 1991-01-23
Also published as: WO1989008603A1; SE8800996L; SE8800996D0; AU3435089A

Abstract

La présente invention se rapporte à un dispositif de serrage de courroie du type comprenant un noyau de serrage de courroie qui est monté pivotant dans une structure et qui, au moyen d'un couplage unidirectionnel, est mis en rotation pas à pas par un levier pivotant. Afin de permettre une manipulation et un fonctionnement aisés du dispositif de serrage tout en assurant des directions de forces favorables, le couplage unidirectionnel de la présente invention comporte également au moins une paire de roues dentées (16, 17), la roue dentée (17) étant reliée au noyau d'enroulement de courroie (2) et l'autre roue dentée (16) étant reliée au levier pivotant. Les centres desdites roues dentées qui s'engrènent l'une dans l'autre coïncident avec les centres de rotation respectivement du noyau d'enroulement de courroie et du levier pivotant, le couplage unidirectionnel étant détachable et destiné à forcer le noyau d'enroulement de courroie à tourner dans la direction d'enroulement de la courroie, lorsqu'on fait pivoter le levier pivotant en direction de la structure.The present invention relates to a belt tightening device of the type comprising a belt tightening core which is pivotally mounted in a structure and which, by means of a one-way coupling, is rotated step by step by a pivoting lever . In order to allow easy manipulation and operation of the clamping device while ensuring favorable force directions, the unidirectional coupling of the present invention also comprises at least one pair of toothed wheels (16, 17), the toothed wheel (17) being connected to the belt winding core (2) and the other gear (16) being connected to the pivoting lever. The centers of said gear wheels which mesh with one another coincide with the centers of rotation of the belt winding core and of the pivoting lever respectively, the unidirectional coupling being detachable and intended to force the winding core belt to rotate in the direction of winding of the belt, when the pivoting lever is pivoted towards the structure.

Description

Strap Tightening Device

The subject invention concerns a strap tightening device comprising a frame which consists of two mutually spaced apart lateral walls, a strap winding-on core bridging the space between said lateral walls and being rotatably mounted in said walls, and a pivotable lever which is drivingly connected to the strap winding-on core via a one-way coupling and which is pivotable relatively to the frame in a plane extending crosswise to the centre axis of said strap winding-on core. Prior-art tightening devices of this kind usually have a drive coupling means which is mounted between the pivotable lever and the strap winding-on core and which comprises at least one cog-wheel which is supported on the strap winding-on core and also one or several spring-biased pawls which cooperate with the teeth of the cog-wheel for engagement therewith. These pawls are arranged to bring along the cog-wheel and thus the strap winding-on core upon movement of the pivotable lever in one direction but to ride above the cog-wheel upon pivotable movement of the lever in the opposite direction.

Strap tightening devices of this kind are often very difficult to use, particulary when they are placed in positions where they are not easily accessible, and this is mainly due to the fact that when the strap is being tightened it becomes necessary to move the pivotable lever in a direction away from the frame, with the result that the tightening device becomes unsteady, because the frame is not backed up by any support, such as e.g. the load to be secured by the strap or any other suitable fixed support face on the load carrier.

The main purpose of the subject invention is to provide an easily mana gable strap tightening device which has none of the disadvantages outlined in the aforegoing. The strap tightening device is characterized therein that the one-way coupling comprises at least one pair of cog-wheels, of which one of the cog-wheels is connected to the strap winding-on core whereas the other cog-wheel is connected to the pivotable lever, the centres of the two intermeshing cog-wheels coinciding with respectively the centre of rotation of the strap winding-on core and the centre of rotation of the pivotable lever, and in that the one-way coupling is releasable and arranged in such a manner that the winding-on core is turned in the strap winding-on direction when the pivotable lever is pivoted in the direction towards the frame.

Two embodiments of the invention will be described in closer detail in the following with reference to the accompanying drawings, wherein Fig. 1 is a lateral view of a strap tightening device in accordance with a first embodiment,

Fig. 2 is a view from above of the tightening device of Fig.

1.

Fig. 3 is a cross section along line III-III of Fig. 2, Fig.4 is a cross section corresponding to Fig.3 but showing the pivotable lever in a winding-on core release position,

Fig.5 is a lateral view of a strap tightening device in accordance with an alternative embodiment,

Fig.6 is a longitudinal sectional view through the device of Fig.5 but shown in an operative, strap tightening position,

Fig. 7 is a view from above of the strap tightening device in accordance with Fig. 5, and

Fig 8 is a partly broken lateral view of the same device seen along line VTI-VII of Fig.7. The strap tightening device illustrated in Figs. 1 - 4 comprises the following principal components, viz. a frame generally indicated by reference numeral 1, a strap winding-on core 2 which is rotationally mounted in the frame 1, and a pivotably mounted lever 3 which by means of a releasable one-way coupling is arranged, when rotated, to bring along the strap winding-on core 2 in its rotational movement to wind-on and tighten the strap 4 intended to be tightened by means of the tightening device. The strap 4 could either extend about the article to be fastened in the form of a continuous loop the two ends 4a', 4a" of which are anchored to the tightening device, as is illustrated in Fig. 1, or else the two strap ends 4a', 4a¹' could be secured independently, for instance to the surface supporting the load to be fastened or in any other suitable manner.

The frame 1 comprises three parallel, spaced apart plates 5, 6 and 7, of which plate 6 and plate 7 preferable are lateral flanges which have been bent upwards from an element of U-shaped cross- -sectional configuration which is bent from a sheet metal blank. The lateral flanges are kept the desired distance apart by means of preferably rivet-pin spacer means 8, 9 and 10, of which spacer means 9 and 10 also bridge the distance between the parallel plates 5 and 6, whereby these parallel plates 5 and 6 will form the side walls of the part of the tightening device which is intended to accommodate the strap 4. The end portions 2b and 2c of the strap winding-on core 2 extend through the end part of the parallel plates 5 - 7, said end portions 2b and 2c merging between the parallel plates 5 and 6 into an enlarged portion 2a, the transitional part between the enlarged port on and the end portions forming an axial abutment face against the facing sides of the parallel plates 5 and 6.

The parallel plate 5 which also forms one of the side walls of the buckle, is pivotably mounted on the spacer pin 9. The end plate 5 is biased against an axial abutment face on the spacer pin 9 by means of a spring washer 11 which on account of its flexibility in combination with the inherent springiness of the plate 5 allows the end wall to be turned away from the winding-on core 2 and be pivoted clockwise in accordance with Fig. 1. When the end wall 5 is pivoted in the opposite direction, i.e. counter-clockwise as seen in Fig. 1, the free end part of the spacer pin 10 serves as a limit abutment means, preventing the end plate 5 from pivoting in this direction beyond the position illustrated in Fig. 1. The strap winding-on core 2 is formed with an axially extending slit 12 which opens into the openable end of the tightening device, which means that the strap 4 may be inserted axially into the winding-on core, when the side wall 5 is pivoted out of the way. To prevent the winding-on core from being compressed at its openable end when the strap is highly tensioned, a stud 13 is formed on the end wall 5, the outer diameter of which is equal to or somewhat smaller than the width of the slit 12. The stud 13 is supported by a tongue member 14 which is punched from the end wall 5 and which projects over the end portion of the strap winding-on core.

The pivotable lever 3 is located in the gap formed between the end plates 6 and 7 and it is journalled in said plates on a shaft 15 which also supports a cog-wheel 16 for rotation therewith. This cog-wheel constantly engages a cog-wheel 17 which is rotatably mounted on the strap winding-on core 2. The pivotable lever 3 is formed with a locking pawl 18 in the form of a rocker plate forming a double lever having its pivot point at 19 and one arm 18a of which is biased by means of a tension spring 20 one end of which is attached to the arm 18a of the rocker plate whereas the opposite end is attached to a pin 21 bridging the gap between the two plate-like spaced-apart side pieces 22 of the pivotable lever 3. The opposite arm 18b of the rocker plate thus tends to engage the cog-wheel 16 as a result of the spring force of spring 20, thereby preventing this cog-wheel from rotating in a clockwise direction as seen in Fig. 3 relatively to the pivotable arm whereas the cog-wheel is allowed to rotate in the opposite direction relatively to the pivotable lever. Portion 18b of the rocker plate 18 projects through essentially triangularly shaped openings 23 formed in the side walls 22 of the pivotable lever. One apex of the triangularly shaped apertures form the rocker plate pivot point 19. A number of rocker plates 24, 25, and 26 are mounted in a corresponding manner in correspondingly triangularly shaped apertures 27, 28 and 29 and one of their end portions is biased by means of associated tension springs 30, 31 and 32, respectively. These springs are attached to the frame by means of cross pins 33, 34 and 35, respecti ely, in such a manner that the rocker plates tend to assume the position illustrated in Fig. 3 wherein they are in engagement with the cog-wheel 17 so as to prevent the latter from rotating counter-clockwise relatively to the frame as seen in Figs. 3 and 4 but to allow it to rotate in the opposite direction. On either side of the cog wheel 17, a release ring 36 is rotatably mounted on the strap winding-on core, said ring having radially projecting abutment fingers 37, 38 and 39, respectively, which are arranged to cooperate with the rocker plates 24-26, and also a radially projecting dog finger 40. In the angular position of the pivotable lever illustrated in Fig. 4 this finger 40 cooperates with and abuts against a cam portion 41 formed on the pivotable lever. The pivotable lever may be blocked in the position illustrated in Fig. 3 by means of a locking member 42 which is arranged for axial displacement in the arm which by means of a spring 43 normally is maintained in the left position as seen in Fig. 3. In this position, the locking member 42 abuts against a limit stop member 44, thus maintaining a catch 45 in engagement with a hook-shaped notch 46 in each one of the two end pieces 6 and 7. An end portion 42a of the locking member 42 extends to the left as seen in Fig. 3, somewhat beyond the rest of the lever. The locking member 42 could be moved against the action of the spring 43 to a second position, in abutment against a limit stop means 47 and in this second position the catch 45 is disengaged from the hook-notch 46, thus allowing the pivotable lever to pivot upwards in relation to the frame 1. The abutment or release ring 36 preferably is spring-biased by spring 48 in the counter-clockwise direction to the position in which the locking rocker plates or pawls 24 - 26 are allowed to pivot into engagement with the cog-wheel 17.

The strap tightening device described in the aforegoing operates in the following manner.

One part 4a' of the strp or a separate strap may preferably be secured to the tightening device beforehand or be wound in loops about the spacer pins 9 and 10, as illustrated in Fig. 1, making the strap self-braking. The end piece 5 is pulled away from the end portion 2b of the strap winding-on core against the action of the spring washer 11 and/or the inherent springiness of the very material of the end piece, and it is then turned away in the clockwise direction as seen in Fig. 1. The strap accommodation slit 12 in the strap winding-on core is now freely accessible from the side of the device. The strap part 4a" may therefore be introduced into the slit formed in the strap winding-on core without the end part of the strap necessarily being accessible. As a result, the strap need not be threaded through the slit. When the strap is introduced into the slit the end piece 5 is returned to the position illustrated in Fig. 1. The strap is now ready to be tightened.

In order to release the pivotally mounted lever 3 the end portion 42a is depressed, whereby the catch 45 is freed. The pivotable lever may now be moved in the clockwise direction. When the pivotable lever pivots about the shaft pin 15 in the clockwise direction, the pawl 18 rides above the teeth of the cog-wheel 16, since the latter cannot take part in this movement because cog-wheel 17 is blocked by the pawls 24 - 26. When the pivotable lever 3 is turned back to the position illustrated in Fig. 3, on the other hand, cog-wheel 16 does take part in this movement, whereby the strap winding-on core is driven by cog-wheel 17 in the clockwise direction as seen in the same figure and consequently the strap part 4a" is wound onto the core from underneath. This is so because this is the direction in which the pawls 24 - 26 ride above the teeth of the cog-wheel 17. By turning the pivotable lever 3 backwards and forwards in this manner, strap material is wound onto the strap winding-on core step by step and the locking pawls 24 - 26 prevent the core from rotating backwards, i the winding-off direction. Upon attainment of the desired degree of tightening the pivotable lever is swung downwards completely, into the position illustrated in Fig. 3, wherein the catch 45 slides along an oblique edge 49 on the frame into engagement with the hook-shaped notch 46. In this position, the pivotable lever is prevented from unintentionally pivoting upwards, away from the frame, for instance during transportation of goods loaded onto a load carrier.

Release of the strap tightening device is effected by pivoting the pivotable lever 3 over centre to the position illustrated in Fig. 4, in which position its abutment cam members 41 abut against the dog fi ngers 40 of the release ri ngs 36 and bri ng al ong the rel ease rings in the cl ockwise di recti on as seen in Fi gs . 3 and 4. In the manner il l ustrated, thi s means that owing to the abutment of the rel ease fingers 37 - 39 against the associated one of locki ng pawl s 24 - 26 the latter are disengaged from the cog-wheel 17 and thus the latter, together with the strap winding-on core 2 , may rotate cl ockwi se as seen in Figs . 3 and 4. This i s made possible because in thi s position of the pivotable lever the pawl 18 sl ides up a cam face 50 formed on the end wal l s 6, 7 of the frame . When the strap wound onto the strap winding-on core 2 has been wound off the latter the strap may be removed from the device, ei ther by being pull ed through the sl i t 12 in the l engthwise direction of the strap or el se the strap may be removed in the lateral di rection after removal of the si de wal l 5 away from the strap winding-on core in the manner described in the aforegoing.

When the pivotable lever 3 has been turned back to the position illustrated in Fig. 4, the release rings 36 are returned by means of the spring 48 to the inactive position illustrated in Fig. 3. By suitable choice of the angular position of the release fingers 37 - 39 relatively to the locking pawls 24 - 26 the spring may be eliminated, i.e. when the angle is such that no self-braking occurs in any position. The gear ratio afforded by the cog-wheel combination 16, 17 means both that a comparatively large force is obtainable to effect the pivotable movement upwards of the lever, although the lever is comparatively short, and also that the tightening of the strap may be effected by the movements of the pivotal lever in the direction towards the tightened strap and against the frame part of the tightening device. In most situations this provides for easy and convenient operation of the device, which often is placed in positions that make it difficult to reach.

Like the embodiment just described the tightening device illustrated in Figs. 5 - 8 comprises a frame which is identified generally by numeral 101, a strap winding-on core 102 and a pivotal lever 103. In accordance with this embodiment the frame 101 is made from two, mutually spaced apart side plates 105 and 106, respectively. The side plates are interconnected by a cross bar 107 having a U-shaped cross-sectional configuration and having end flanges 107a which extend through openings formed in the side plates 105, 106 and secured in position in said openings by up-ending of the material. The strap winding-on core 102 consists of two rods 102a and 102b which have a cross-sectional shape in the form of segments of a circle and which are formed with flat faces 102a¹ and 102b', respectively, arranged in facing relationship. On the exterior face of the side plates 105 and 106, respectively, the two strap winding-on core sections pass through apertures of corresponding configuration which have been made in two cog-wheels 108 and 109, respectively. The two cog-wheels retain the two sections in a spaced apart relationship, whereby a slit 110 is formed which extends all the way along the strap winding-on core. Through this slit, the strap 104 to be wound onto the core is intended to be inserted. On the exterior of the cog-wheels 108, 109 borings are formed in each one of the end portions of the two sections 102a and b of the strap winding-on core for insertion therethrough of locking pins 111 and 112, respectively, to maintain the two core sections and the cog-wheels in position. The locking pins 111, 112 preferably are tubular members which are radially expandable and formed with lengthwise extending slits. The pivotable lever 103 is pivotably mounted in the frame 101 on a shaft 113 and consists of plate-like side pieces 114 and 115, one on either si e of the side pieces of the very frame, and spaced a sufficient distance apart to allow also the associated cog-wheels 116 and 117 to be accommodated therein, these cog-wheels being mounted on the shaft 113 for rotational movement relatively to the frame 101 as well as to the pivotable lever 103. A rocker pawl 118 extends between and is mounted in the two side pieces 105, 106 of the pivotal lever and form a double lever with its fulcrum in point 119. One of the arms of the lever is biased by a traction spring 120 tending to maintain the opposite arm in engagement with the cog-wheels 116, 117. The pawl 118 is directed in such a manner relatively to the cog-wheels 116, 117 that the pivotal arm 103 carries along the cog-wheels in its movement counter-clockwise as seen in Fig. 8, for example, whereas the pawl rides above the cog-wheel theeth when the pivotal lever 103 is turned clockwise in accordance with the same drawing figure. Reference numeral 121 designates a locking element which extends between the side pieces 105, 106 of the frame and which is pivotally mounted therein, said locking element being maintained in engagement with the cog-wheels 108, 109 that are mounted on the strap winding-on core. The locking element 121 penetrates through the side pieces of the frame sufficiently far to cross the planes in which the pivotal lever side pieces 114, 115 are positioned. The side pieces of the pivotal lever which are interconnected at the free end of the pivotal lever by means of a spacer member in the form of a sleeve 123 and pin 124 passing therethrough, present adjacent the pivotally mounted end of the lever a release finger 125. When the pivotal lever is pivoted to an over-centre position past its normal strap tightening position, i.e. the position illustrated in Fig. 5, this finger comes into contact with the locking element 121 for the purpose of displacing the latter against the action of the spring 122, away from the cog-wheels 108, 109 for the purpose of releasing the strap 104 which is wound onto the strap winding-on core.

In the side pieces of the pivotal lever is displaceably mounted a locking means 126 to which the opposite ends of the traction springs 120 are attached, thus tending to maintain the locking means 126 in the displaced locking position illustrated in Fig. 8, in which the latter engages a notch 127 formed in the frame side pieces. A dog finger 131 extends between the locking means 126 and a depending finger 118a on the pawl 118, said finger 131 providing unrestricted movement space for the pawl during normal use but upon actuation by the locking means 126 in the release direction, i.e. to the left as seen in Fig. 8, causes the pawl 118 to be disengaged from the cog-wheels 117. The disengagement is made possible because of clearances 132 and 133 formed in the follower means. In order to effect automatic displacement of the locking means 126 to the left in accordance with Fig. 8 upon pivotal movement of the pivotal lever 103 to the position illustrated in Fig. 8, the side pieces 114, 115 present oblique edges 128 on which the locking means 126 slides upon turning down of the pivotal lever in order finally to snap into engagement with the notch 127. The lateral pieces of the pivotal lever also are formed with an abutment cam 129 which in the locked position illustrated in Fig. 8 abuts against the locking element 121, thus locking the latter in its position of engagement for the purpose of preventing unintentional release of the tightened strap. Fig. 6 illustrates the manner in which a strap part 104a' is permanently fastened to a cross bolt 130 which extends between the frame side pieces.

The strap tightening device in accordance with the second embodiment operates in the following manner:

When a strap 104 is to be tightened with the aid of the tigthening device in accordance with the invention the end part 104a" thereof is passed through the slit 110 formed in the strap winding-on core, whereupon the pivotal lever is pivoted backwards and forwards between the position illustrated in Fig. 6 and a position wherein the locking means 126 does not engage in the notch 127. When the pivotal lever is moved in the direction indicated by arrow 134 in Fig. 6, the cog-wheels 116, 117 are forced in the counter-clockwise direction as seen in Figs. 5 and 6 and 8, whereby the cog-wheels 108, 109 and thus the strap winding-on core 102 are urged in the clockwise direction while the locking element 121 rides above their teeth crests against the action of the spring 122. When the desired strap tension has been achieved, the pivotal lever is turned downwards to the position illustrated in Fig. 8, wherein the locking means 126 has been moved into engagement with the blocking notch 127 and the locking cam means 129 are in engagement with the locking element 121 as illustrated in Fig. 8, thus efficiently preventing the strap winding-on core from rotating in a strap winding-off direction and thus also efficiently preventing unintentional generation of slack in the strap. When the strap is to be released, the locking means 126 is moved to the left as seen in Fig. 8 and is then disengaged from the blocking notch 127 while at the same time the pawl 118 via the dog finger 131 is disengaged from the cog-wheels 117. The pivotal lever 103 is then pivoted clockwise until its release finger 125 contacts that face of the locking element 121 that faces the cog-wheels 108, 109, lifting this element out of its engagement with the cog-wheels, whereupon the strap winding-on core together with its cog-wheels and thus also cog-wheels 116, 117 on the pivotal lever are allowed to turn freely. Reference numeral 132 designates a cam means formed on the side pieces of the frame which in the release position shown in Fig. 5 cooperates with and abuts against the pawl 118, lifting the latter out of its engagement with cog-wheels 116, 117 with the result that the latter cannot be braked but are allowed to turn freely, whereby the strap may be wound off the strap winding-on core without any significant resistance.

The invention is not limited to the embodiments described in the aforegoing and illustrated in the accompanying drawings as examples only but its various detail components may be altered in a variety of ways within the scope of the appended claims without departing from the inventive idea. For instance, the tigthening device may be made from another material than the sheet metal material to which reference is made in the aforegoing and as shown in the drawings. Thus the tightening device or component parts thereof could be castings which means that the parts involved are given a different configuration. Also other types of modifications are possible within the scope of the invention without departing from the inventive idea thereof. The dimensions of the two cog-wheels making up the cog-wheel pairs may be varied in many ways to achieve a suitable gear ratio in relation to the length of the pivotal lever.

Claims

1. A strap tightening device comprising a frame (1; 101) consisting of two mutually spaced apart lateral walls (5, 6; 105, 106), a strap winding-on core (2; 102) bridging the space between said lateral walls and being rotatably mounted in said walls, and a pivotable lever (3; 103) which is drivingly connected to the strap winding-on core via a one-way coupling and which is pivotable relatively to the frame in a plane extending crosswise with respect to the centre axis of said strap winding-on core, c h a r a c t e r- i z e d t h e r e i n that the one-way coupling comprises at least one pair of cog-wheels (16, 17; 108, 116; 109, 117) of which one of the cog-wheels (17; 108, 109) is connected to the strap winding-on core and the other cog-wheel (16; 116, 117) is connected to the pivotable lever, the centres of the two intermeshing cog-wheels coinciding with respectively the centre of rotation of the strap winding-on core and the center of rotation of the pivotable lever, and in that the one-way coupling is releasable and arranged in such a manner that the winding-on core is forced to turn in the strap winding-on direction when the pivotable lever is pivoted in the direction towards the frame .

2. A strap tightening device as claimed in claim 1, c h a r a c t e r i z e d t h e r e i n that the one-way locking means affecting the two cog-wheels are releasable manually.

3. A strap tightening device as claimed in claim 2, c h a r a c t e r i z e d t h e r e i n that the locking means (24 - 26; 121) acting on the cog-wheels of the strap winding-on core are releasable against the action of a spring by means of an abutment member (41; 125) on the pivotable lever (3; 103), which directly or indirectly comes into contact with said locking means when the pivotable lever is pivoted to a position externally of the normal strap winding-on area of pivotment.

4. A strap tightening device as claimed in claim 3, c h a r a c t e r i z e d t h e r e i n that locking means acting on the cog-wheel of the strap winding-on core and the cog-wheels of the pivotable lever are arranged for release by cooperating with and abutting against cam means provided on respectively the pivotal lever and the strap tightening device frame, when the pivotal lever is moved to its release position.

5. A strap tightening device as claimed in claim 4, c h a r a c t e r i z e d t h e r e i n that at least one driver ring (36) which is rotatably mounted on the strap winding-on core is arranged for transferring the release movement from the pivotal arm cam means to the locking means acting on the cog-wheel of the winding-on core, said ring positioned adjacent the winding-on core cog-wheel (17) and presenting around its periphery one radially projecting dog finger (40) arranged to cooperate with and abut against said cam means (41), and also a number of likewise radially projecting release fingers (37 - 39), the number of release fingers being equal to the number of locking pawls distributed about the periphery of said cog-wheel, said release fingers (37 - 39) being so positioned and so dimensioned that upon turning movement of said driver ring they abut against its respective one of said locking pawls (24 - 26), moving the latter to a position of release of said cog-wheel.

6. A strap tightening device as claimed in claim 5, c h a r a c t e r i z e d t h e r e i n that said pivotal lever is formed with an abutment face (129) which in the blocked locking position of said pivotal lever (103) is positioned behind a locking element (121) engaging with the cog-wheel of the strap winding-on core, thus preventing the element from moving to a position of release of the cog-wheel (108, 109).

7. A strap tightening device as claimed in any one of the preceding claims, c h a r a c t e r i z e d t h e r e i n that the locking pawls (24 - 26, 18; 121, 118) are spring biased rocker plates which are mounted in apertures formed in lateral flanges on the frame (1; 101) and the pivotal lever (3; 103), respectively, end parts of said rocker plates arranged to project through said apertures.

8. A strap tightening device as claimed in any one of the preceding claims, c h a r a c t e r i z e d t h e r e i n that the pivotal arm (3) is mounted adjacent one of the side walls (6, 7) whereas the opposite side wall (5) is arranged to be opened in the area of the strap winding-on core (2) so as to form a lateral aperture through which the strap to be tightened by means of the tightening device may be introduced laterally of the latter.

9. A strap tightening device as claimed in claim 8, c h a r a c t e r i z e d t h e r e i n that at a distance from the strap winding-on core the openable side wall (5) is pivotable in a plane extending crosswise relatively to the centre axis of the strap winding-on core, by being mounted on one end portion of a pin (9) the opposite end portion of which is retained by the opposite side wall (6, 7), said pivotable side wall (5) forming a seat for and being disconnectable from one end portion (2b) of the strap winding on core.

10. A strap tightening device as claimed in claim 9, c h a r ac t e r i z e d t h e r e i n that the part of the pivotable side wall (5), in which said strap winding-on core (2) is mounted, is spring-biased towards an active mounting position and arranged to be released manually against the action of the spring bias in the longitudinal direction of the strap winding-on core away from the latter, said strap winding-on core also being formed with a strap slit (12) extending alongside the core and opening towards the openable side.