Device for stretching case ribbons of plastic material

[57] ABSTRACT

A device for stretching case ribbons of plastic material, having a clamping device for the one ribbon end, a cutting device and stretching mechanism for the other ribbon end and an actuating lever for the stretching mechanism and cutting device, the device being made of simple and cheap molded plastic parts combined with stamped metal parts, and said clamping device having clamping jaws of which the one only is toothed thereby allowing easy operation of the clamping device and careful treatment of the ribbon.

Claims, 3 Drawing Figures

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Patented May 16, 1972

3,662,790

F1G.1

Sheets-Sheet 1

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INVENTOR.

BY

Patented May 16, 1972

3,662,790

Sheets-Sheet 2

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INVENTOR.

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3,662,790

2

DEVICE FOR STRETCHING CASE RIBBONS OF PLASTIC MATERIAL

This invention relates to a device for stretching case ribbons of plastic material.

Prior devices of this kind have a clamping device for the one ribbon end, a cutting device and a stretching mechanism for the other ribbon end and an actuating lever for these parts, whereby all parts of the device are made of metal. Amongst these elements are relatively expensive and heavy turned and cast parts. The device has a number of parts operating under substantial load, it being necessary to temper such parts. Therefore, no possibility was found in the past for simplifying the construction and reduce the price. The clamping devices of prior stretching devices are unsatisfactory because they tend to damage the ribbon and require high actuating forces.

It is an object of this invention to overcome these disadvantages of prior devices. The device according to this invention basically differs from the prior devices in thatsaid damping device and stretching mechanism have shafts of plastic material interconnected with metallic actuating parts, said cutting device has a cutting blade mounted in a support of plastic material, and said clamping device has afirst eccenterlike rotatable clamping jaw and a second clamping jaw, the clamping surface of the second clamping jaw only being toothed for improving the clamping effect. Therefore, instead of the expensive and heavy turned and cast metallic parts of prior devices, cheap and relatively light parts of plastic material and stamped metal parts may be used, whereby combination of such parts is feasible such that all parts are suitable for the stresses acting on them. By the use of plastic parts and stamped parts the weight may substantially be reduced.

The clamping device is reliable without damaging the ribbon and it may easily be operated. Preferably said second clamping jaw may be displaceable between stops in a direction transversal to the clamping force, and it may be urged or restored into a rest position by a spring. In this way a further substantial improvement of the clamping action,.careful treatment of the ribbon and ease in operation may be obtained.

This invention will now be explained in detail with reference to the accompanying drawing illustrating by way of example an embodiment of the stretching device.

FIG. 1 is a side view,

FIG. 2 is a partial vertical section and

FIG. 3 is a partial horizontal section of the device.

The illustrated device has a frame made of stamped parts, including a base plate 1 and an extension 2 serving as a handle and support. The frame has two side walls 3 and 4 and thus has substantially U-shaped cross section. The movable parts of the device are mounted on side walls 3 and 4.

The clamping device for the one end S' of the case ribbon 5 to be stretched and indicated in dash-dotted lines, has a shaft 6 of plastic material pivoted in side walls 3 and 4. Outside the side wall 3 the shaft has a clamping jaw 7 with a slightly eccentric smooth clamping surface 7'. The clamping jaw 7 is located above the toothed rear end of a second stamped clamping jaw 8 mounted in a slider 9 of plastic material. A resetting spring 10 usually urges the slider 9 into the rest position shown in FIG. 1. This end position of the slider 9 and its opposite end position are determined by abutment of the: bent nose of the clamping jaw 8 against the end surfaces of a window 11 of plate 1. The slider 9 is guided and anchored to the plate 1 by means of a disc 12.

The shaft 6 has a coarse external toothing 13 at an end portion thereof. Cam rings 14 having a corresponding inner toothing engaging the external toothing of the shaft 6 are mounted on shaft 6. The cam rings 14 are axially secured between a shoulder of the shaft and the side wall 4. As shown in FIG. 2, the cam rings have a nose 15 and an extension 16. An anchoring pin 17 for the one end of a coil spring 18 wound onto shaft 6 is riveted to the extension 16. The other end of spring 18 is supported on the base plate 1 so that spring 18 tends to turn cam rings together with shaft 6 in counterclockwise direction, whereby the eccentric clamping surface

7' is swung downwardly against the toothed portion of the lower clamping jaw 8.

By means of bushings 21 a stretching or spanning shaft 22 of plastic material is pivotably mounted in side walls 3 and 4. It 5 has an external toothing 23 similar to toothing 13. Stamped discs 24 having an external ratchet toothing engage the toothing 23 of shaft 22 with an internal: toothing and are thus fixed on shaft 22. Discs 24 are axially secured between a shoulder of shaft 22 and a ring 25 shifted onto shaft 22, ¹⁰ whereby shaft-22 is itself axially secured by means of a button 26 of plastic material held in the hollow end portion of shaft 22 by a snap joint. The free end of shaft 22 extending outwardly from side wall 3 has an external toothing and a ., diametral slit 27 allowing insertion of the one end of ribbon 5 with little clearance.

A stamped actuating lever 29 is pivotably mounted on shaft 22 and a ring 25 shifted thereon by means of two annular lugs 28, Two metal sheets welded to the inside of the actuating 2Q lever form a recess 31 slightly relieved at one end, into which a stepping pawl 32 and a V-shaped leaf spring 33 maintaining pawl 32 in engagement with the ratchet toothing of discs 24 are loosely inserted and mounted in recess 31. Spring 24 engages a stop nose 34 formed in the stepping pawl 32. A stop 25 pawl 35 with leaf spring 36 is mounted in a similar manner on the base plate 1.

Ablade support 38 of plastic material is fixed on the frame. It has a lateral slit 39 for receiving the ribbon 5, and a cutting blade 40 with a slit 41 is molded into the support 38 within 30: reach of slit 39. A cutting shaft 42 is pivoted in a longitudinal bore of the blade support 38, this shaft 42 engaging blade 40 without clearance within reach of a slightly inclined surface ground on shaft 42 and forming a cutting edge 43. The other end of the cutting shaft 42 is pivoted in side wall 4. Inside the 35 bearing in side wall 4 shaft 42 has a plane cuttings 44. Two similar stamped discs 45 having each a nose 46 and a hole of a form similar to the cross section of the shaft 42 within reach of the cuttings 44 are mounted on shaft 42. Discs 45 form an actuating cam of which the nose 46 extends into a gap 47 of the 40 one ring 28 of the actuating lever 29. The illustrated rest position of discs 45 and of the cutting shaft 42 is determined by engagement of the one straight edge portion of discs 45 with the baseplate 1.

When the actuating lever 29 is in its lower end position as il45 lustrated, a downwardly extending nose 48 of the same engages extension 16 formed by rings 14 and thereby maintains such rings and shaft 6 in the illustrated position in which the clamping surface 7' is lifted off the lower clamping jaw 8.

When the device is in its initial position as illustrated, the one end 5' of the case ribbon is inserted between the clamping jaws 7 and 8 and below the blade support 38. The other end 5 of the ribbon is inserted into the slit 38 of the blade support 38 and into the slit 41 of the blade 40 respectively, and then ₅₅ into the slit 27 of the stretching shaft 22. A seal 49 is applied onto the overlapping ribbon ends, this seal being closed after stretching of the ribbon in the manner set out hereafter. If possible, the seal may also be applied after stretching. In order to stretch the ribbon, the actuating lever 29 is lifted. Its nose ¢0 47 first releases extension 16 and the clamping shaft 6 is turned in counterclockwise direction by spring 18. Hereby the clamping surface 7’ of the clamping jaw 7 is pressed against the toothed portion of the lower clamping jaw 8 whereby the ribbon end 5' is firmly clamped between jaws 7 and 8. Lifting 65 of the actuating lever 29 has caused rotation of the stretching shaft 22 in counterclockwise direction due to transmission of the lever movement through paw] 32 and discs 24. By repeated oscillating movement of the actuating lever 29 within a range for which neither the cutting device is actuated through 70 discs 45 nor the clamping shaft is rotated through extension 16, the stretching shaft is further rotated stepwise in clockwise direction, whereby the ribbon end 5 is wound onto the stretching shaft and the ribbon is stretched. By the increasing tension of the ribbon the clamping jaws 7 and-8 are shifted to 75 the right and are thus increasingly wedged against each other.

3,662,790

Since the ribbon cannot slide on the toothing of the clamping jaw 8, damaging and weakening of the same is avoided. Indentation of ribbon by the toothing of clamping jaw 8 only occurs at the inner side of the tape and is not visible. When the ribbon is sufficiently stretched, the seal 48 is closed, whereafter the lever 29 is turned in anticlockwise direction until the nose 46 of disc 45 abuts against the one end of the gap 47 and is turned together with discs 45 and cutting shaft 42 in clockwise direction. The ribbon end 5 is thereby cut off by interaction of one cutting edge formed at the slit 41 of blade 40 and the cutting edge 43 of cutting shaft 42. The tape end now gets loose on the stretching shaft and may be removed from the same. The actuating lever 29 is now rotated downwardly into the illustrated initial position, whereby its nose 47 engages the extension 16 and turns the clamping shaft 6 back into its illustrated inoperative position. The clamping jaw 7 is thus lifted off the clamping jaw 8 and the ribbon portion 5' may now be removed from the device. Returning of the clamping jaw 7 from its clamping position into its illustrated initial position is substantially facilitated by the smooth claming surface 7' sliding on the ribbon and the possibility to shift the lower clamping jaw 8 back from its clamping position.