US2511305A - Pulling and stretching device - Google Patents

Description

June 13, 1950 s. A. TELL 2,511,305

PULLING AND ,STRETCHING DEVICE Fiied Sept. 26, 1947 2 Sheets-Sheet 1 267 28 :;y- -17 g 'go -29 57 2# rag 25 j 1 June 13, 1950 s, TELL 2,511,305

PULL-INC AND STRETCHING DEVICE Filed Sept. 26, 1947 2 Sheets-Sheet 2 Patented June 13, 1950 PULLING AND STRETCHING DEVICE Sven Axel Tell, Akeslund, Sweden, assignor to Ingenjorsfirman Ljung & Lindqvist, Stockholm,

Sweden Application September 26, 1947, Serial No. 776,210 In Sweden September 30, 1946 10 Claims.

This invention relates to a pulling and stretching device for ropes or similar members, which includes two gripping devices displaceable relative to each other in the longitudinal direction of the rope and adapted alternatingly to be brought into tight engagement with the rope.

Devices of this type hitherto known which in the manner indicated climb on the rope are constructed in a manner such that their indented grippers are trailing on the rope even when they are not tightly engaging the rope during their return movements along the same, with the result that the rope will be damaged and the grip-- pers worn out, and the spaces between the indentations will soon be filled with particles from the rope so that the grippers become inoperative.

The object of my invention is to eliminate the above inconvenience and to provide an improved construction of pulling and stretching device in which the grippers are always kept clear of the rope when the appertaining gripping device has to be moved relative to the rope. I attain this object and further objects by mechanism illustrated in the accompanying drawings in which- Fig. 1 illustrates a side elevation of the rope stretching device; Fig. 2 is an enlarged lateral view of one of the gripping devices; Fig. 3 is a section taken on the line III-III in Fig. 2; Fig. 4 is a section on the line IV-IV in Fig. 2; and Figs. 5-7 illustrate various positions of the control and gripping members at different phases of operation.

Referring to the embodiment illustrated in Fig. 1, reference numeral I denotes a support for the stretching device. The support I is provided with an opening 2 by means of which the apparatus can be secured to a suitable stationary member, such as a tree stump not shown in the drawing. A lever 4 having a suitable handle is pivotally mounted on the support I by means of a pin 3. At a relatively short distance from the pin 3, an arm 6 is pivotally mounted on the lever 4 by means of a pin 5. The arm 6 is provided with pins 1 and 8 on which links 9 and I0, respectively, are mounted, said links appertaining to the gripping device generally denoted at a. The other gripping device I) is by means of similar pins and links mounted at the outer end of the support I.

During operation of the apparatus, the gripping devices a and b are alternately brought into tight engagement with a rope 35 to be pulled or stretched. When the lever 4 is swung to the right in Fig. 1, the gripping device a will engage the rope which will be moved accordingly to the 2 right. When the lever is moved back to the left, the gripping device a will be released from the rope and the gripping device 12 will engage the rope and maintain the same in its position.

The construction of the gripping devices will now be described with reference to Figs. 2-4. Since the construction and mode of operation of both gripping devices are substantially identical, the gripping device b only will be described in detail.

The links 9 and Ill are by means of pins II articulated to suitably indented grippers I2 and I3 adapted to cooperate with the rope to be stretched. The member 9, I0, I2, I3 constitute a link system in the shape of a parallelogram. It will be seen that if the links 9, Ii! are swung in an anti-clockwise direction as viewed in Fig. 2, the grippers I2 and I3 will be moved towards each other, whereas a swinging movement of the links 9 and iii in the opposite direction will result in that the grippers will be removed from each other.

By means of keys I l, the pins I I are prevented from rotation relative to the links 9 and I 0. Outside the grippers I2 and I3, finger-like members I5 are firmly secured on the pins II. The fingers I5 constitute guards at the edge of the rope-receiving space between the grippers as they serve to prevent the rope from sliding laterally out of the space between the grippers. If the links 9 and II] are swung in a clockwise direction as viewed in Fig. 2, the fingers I5 will be turned away from the opening between the grippers so that the rope can be placed into or removed from the space between the grippers.

On the pins II for the gripper it there is mounted an arm I6 which at its outer end carries a casing I'l. Alternatively, the arm It may be made in a single piece with the gripper I3. In order to prevent the various parts from sliding off the pins ll, there is provided a plate I8 having two notches. The edges IQ of the notches engage recesses 2B on the pins II. The plate is is secured in place by means of a stop screw 26. On the pins II for the gripper I2 is mounted an arm 22 which at its outer end is formed as an abutting member 23. On the pins I! there is also mounted a stop plate I8. The members I6, I! and 22, 23 will be moved integrally with the grippers l3 and I2 respectively, as if they would be of a single-piece construction.

In the casing I! located at some distance from the grippers, a sleeve 25 is displaceable in a guide member 24, and a rod 21 is displaceable in a guide member 26. The rod 21 has a projection 2s and between said projection and the bottom of the sleeve 25 there is inserted a helical spring 23. The sleeve is provided with an abutting member 30 for cooperation with an abutting member 3| in the casing ll. By means of a stop nut 32, two abutting members .33 and 3d are secured to the rod 2?. The abutting member 34 is arranged for cooperation with the abutting member 23.

The sleeve 25 and the abutting member 33 constitute a pair of jaws adapted to engage opposite sides of the rope placed into the gripping device, said jaws being urged towards each other by means of the spring 29. The opposite faces of the jaws are advantageously smooth so as not to damage the rope.

Ihe mode of operation of the apparatus described is as follows.

In order to insert the rope to be pulled or displaced into the gripping devices, said devices are manually moved towards the right as viewed in Fig. 1 so as to swing the links 9 and ID in a clockwise direction. As a result thereof, the grippers are moved from each other to enable the rope to be placed into the spaces therebetween. When the grippers are removed from each other, also the arms 13 and 22 will be displaced from each other. When the abutting member 23 engages the abutting member 34, the rod 2? and the jaw 33 will be moved downwardly. Due to the engagement of the abutting members $3 and ti, the jaw 25 will be moved upwardly together with the casing H, the jaws being consequently moved apart from each other into the positions shown in Fig. in which the rope '35 can be placed between the jaws.

To the left in Figs. 5-7, the corresponding positions of the gripping members 12 and i3 are indicated in their different corresponding positions.

After the rope has been inserted the gripping devices are manually moved back into their original positions. The jaws now have the positions shown in Fig. 7 in which they are maintained in engagement with the rope 35 under the influence of the spring 29, whereas the grippers l2, l3 are not yet entirely forced against the rope. As will be seen from the drawing, the abutting members 36, 3! and 23, 3 3 are arranged such that the jaws 25 and 33 may abut against the rope, while the grippers are still in positions clear of the rope.

If now the lever 3 is moved to the right as viewed in Fig. i, the frictional engagement between the jaws 25, 33 and the rope 35 (Fig. '7) will give rise to a tension in the arm it of the gripping device a, and said tension will cause the links 3 and Hi to swing in a clockwise direction about their pivots I and 8, respectively, with the result that the grippers l2, 13 of the gripping device a will be tightly forced against the rope 35, as indicated in Fig. 6. In this position, the abutting member 23 has been removed from the abutting member 34, the pressure exerted by the spring 29 being consequently entirely taken up by the rope 35. Due to the fact that the jaws 25, 33 in this position constitute a unit freely guided in the casing ii, the spring 29 cannot exert any undesired separating action upon the grippers. Consequently, the rope 35 will be firmly grasped between the grippers and the entire pulling force in the rope will be taken up by the grippers.

During this phase of operation the gripping device b is inoperative. During the movement of the lever 4 towards the right the rope grasped by the gripping device 0: is pulled through the gripping device b. The jaws 25, 33 of the last named gripping device are in frictional engagement with the rope and consequently tend to move towards the right. However, due to the swinging movement of the links 9 and ill of the gripping device I) in the clockwise direction, the grippers of said gripping device will tend to move still more apart from each other. As a conseguence, the pressure between the abutting members 30 and 3t and between the abutting members 23 and 34 will be increased (Fig. '7). The abutting pressure of the jaws 25 and 33 tends to decrease, and a posit-ion of equilibrium will arise in which the movement of the grippers from each other will cease. In this position, the jaws of the gripping device I) are abutting the rope at a reduced pressure, while the grippers are kept clear of the rope which consequently will not be damaged as it passes between the grippers. As a result of the spring 29 inserted between the jaws 25 and 33 the operation of the apparatus is independent of the diameter of the rope 35. During the movement of the gripping device relative to the rope the gr ppers will always be held entirely out of engagement with the rope.

When the rope has been moved towards the right through a distance depending upon the stroke of the lever 4, said lever is moved back towards the left as viewed in Fig. 1. During this backward movement, the rope tends, to begin with, to move towards the left through the gripping device 1). In a manner similar to that described above with reference to the gripping device a, the jaws 25, 33 of the gripping device I) now cause the grippers to engage the rope, while the grippers of the gripping device a are opened in the same manner as previously described with reference to the gripping device I), the gripping device a being consequently moved towards the left along the rope kept in position by the other gripping device. Thereupon, the operation is repeated, and the rope will be pulled one step during each stroke to the right of the lever 45.

In the above description it was supposed that the rope has to be stretched or moved together with a load from the left to the right as viewed in Fig. 1. If instead thereof the tension of the rope should be lessened ,or the load be lowered, that is, if the rope should be pulled in the opposite direction, and if the gripping device .a is supposed to engage the rope, the working stroke .01 the lever '4 will be directed to the left. In this case, the gripping device '0 is to be manually moved such that its grippers are disengaged from the rope, the jaws 25 and 33 being then in the positions shown in Fig. '7'. When the lever reaches its end position, the gripping device I) is released and will then be forced into eng gement with the rope in the manner described above, While the gripping device a is manually released and the lever 'is'moved back to the right hand end position. It will be obvious that the'gripping devices need not be manually actuated, but may instead thereof be shifted by means of a wire or similar member suitably connected to an actuating device, such as a movable-handle on the lever 4, by means of which the gripping devices can be displaced in the desired direction during the movement of the lever.

What I claim is:

-1. In "a rope pulling and stretching device, two gripping devices displaceable relative to "each other substantially longitudinally of the rope to be pulled and stretched, each-of said gripping devices including at least two grippers, a control device having jaws in frictional contact with a I direction.

2. In a rope pulling and stretching device, two gripping devices displaceable relative to each other substantialy longitudinaly of the rope to be pulled and stretched, each of said gripping devices including at least two grippers, a control device constructed and arranged frictionally to contact a rope placed between said grippers, and means for connecting said control device with said grippers to remove said grippers from each other in response to a movement of said rope in a certain direction and to force said grippers towards each other in response to a movement of said rope in the opposite direction, said control device comprising two jaws movable towards and away from the rope, and resilient means for forcing said jaws into frictional contact with the rope.

3. In a rope pulling and stretching device, two gripping devices displaceable relative to each other substantially longitudinaly of the rope to be pulled and stretched, each of said gripping devices including at least two grippers, a control device constructed and arranged frictionally to contact a rope placed between said grippers,

and means for connecting said control device with said grippers to remove said grippers from each other in response to a movement of said rope in a certain direction and to force said grippers towards each other in response to a movement of said rope in the opposite direction, said control device comprising two jaws movable towards and away from the rope and having comparatively smooth abutting faces, and resilient means for forcing said jaws into frictional contact with the rope.

4. In a rope pulling and stretching device, two gripping devices displaceable relative to each other substantially longitudinally of the rope to be pulled and stretched, each of said gripping devices including a link system having links articulated to each other to form a parallelogram, two opposite links of said system constituting a pair of grippers for the rope, and a control device having jaws in frictional contact with a rope placed between said grippers, and means actuated by the frictional engagement between the rope and said jaws for connecting said control device with said link system to remove said grippers from each other in response to a movement of said rope in a certain direction and to force said grippers towards each other in response to a movement of said rope in the opposite direction.

5. In a rope pulling and stretching device, two gripping devices displaceable relative to each other substantially longitudinally of the rope to be pulled and stretched, each of said gripping devices including at least two grippers, a control device constructed and arranged frictionally to contact a rope placed between said grippers, and means for connecting said control device with said grippers to remove said grippers from each other in response to a movement of said rope in a certain direction and to force said grippers towards each other in response to a movement of said rope in the opposite direction, said control device comprising two jaws movable towards and away from the path of the rope, a guide member for said jaws extending at an angle to the path of the rope, and resilient means for forcing said jaws into frictional contact with the rope.

6. In a rope pulling and stretching device, two gripping devices displaceable relative to each other substantially longitudinally of the rope to be pulled and stretched, each of said gripping devices including at least two grippers, a control device constructed and arranged frictionally to contact a rope placed between said grippers, and means for connecting said control device with said grippers to remove said grippers from each other in response to a movement of said rope in a certain direction and to force said grippers towards each other in response to a movement of said rope in the opposite direction, said control device comprising two parallel guide members connected with one of said grippers, a rod axially displaceable in one of said guide members, a member secured to said rod, said member constituting one jaw of a pair of jaws, a second jaw displaceably mounted in the other one of said guide members, a projection on said rod, and resilient means between said second jaw and said projection for moving said jaws towards each other.

7. In a rope pulling and stretching device, two gripping devices displaceable relative to each other substantially longitudinally of the rope to be pulled and stretched, each of said gripping devices including at least two grippers, a control device constructed and arranged frictionally to contact a rope placed between said grippers, and means for connecting said control device with said grippers to remove said grippers from each other in response to a movement of said rope in a certain direction and to force said grippers towards each other in response to a movement of said rope in the opposite direction, said control device comprising two parallel guide members connected with one of said grippers, a rod axially displaceable in one of said guide members, a members secured to said rod, said members constituting one jaw of a pair of jaws, a second jaw displaceably mounted in the other one of said guide members, a projection on said rod, resilient means between said second jaw and said proj ection for moving said jaws towards each other, an abutting member on each of said grippers, and an abutting member on each of said jaws, said abutting members being constructed and arranged to move said jaws from each other upon movement of said grippers to a certain distance from each other.

8. In a rope pulling and stretching device, two gripping devices displaceable relative to each other substantially longitudinally of the rope to be pulled and stretched, each of said gripping devices including at least two grippers, a control device constructed and arranged frictionally to contact a rope placed between said grippers, and means for connecting said control device with said grippers to remove said grippers from each other in response to a movement of said rope in a certain direction and to force said grippers towards each other in response to a movement of said rope in the opposite direction, said control device comprising two parallel guide members connected with one of said grippers, a rod axially displaceable in one of said guide members, a

jaw displaceably mounted in the other one of said guide members, a projection on said rod, re silien-t means between said second jaw and said projection for moving said jaws towards .each other, an abutting member on each of :said grippers, and an abutting member on each of said jaws, said abutting members being constructed and arranged to move said jaws from each other upon movement of said grippers to a certain distance from each other and to move said jaws concurrently as a unit in said guide members when said grippers are engaging said rope.

9. A rope pulling and stretching device including a support, a lever pivotally mounted on said support, and two gripping devices displaceable relative to each other, one .of said gripping devices being connected to said support and the other gripping device being connected to said lever, each of said gripping devices including at least two grippers, a control device constructed and arranged frictionally to contact a, rope placed between said grippers, and means for connecting said control device with said grippers to remove .sa-id grippers from each other in response to va movement of said rope in a, certain direction and to force said grippers towards each other in response to a movement of said rope in the opposite direction.

10. In a rope pulling and stretching device, two gripping devices displaceable relative to each other substantially longitudinally of the rope to be pulled and stretched, each .of said gripping devices including a link system having links articulated to each other to form a parallelogram, w pp e links of said system constituting a pair of grippers for the rope, guard projections secured to the other two opposite links and constructed and arranged in the gripping positions ,of said grippers to project across the edge of the rope-receiving space between said grippers and upon removal of the grippers from each other to move out of lateral alinement with said rope-receiving space, and a control device associated with one of said grippers to remove said grippers from each other in response to a movement of said rope in a certain direction and to iorce said grippers towards each other in response to a movement of said rope .in the opposite direction.

SVEN AXEL TELL.

Country Date Australia Nov. 6, 1944 Number Certificate of Correction Patent No. 2,511,305 June 13, 1950 SVEN AXEL TELL It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 6, line 45, for the word members both occurrences, read member;

and that the said Letters Patent should be read with these corrections therein that the some may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 29th day of August, A. D. 1950.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

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