US3641857A

US3641857A - Rotary cutting head for wrapping machine

Info

Publication number: US3641857A
Application number: US5077*[A
Authority: US
Inventors: Jerome J Vande Castle
Original assignee: FMC Corp
Current assignee: FMC Corp
Priority date: 1970-01-22
Filing date: 1970-12-22
Publication date: 1972-02-15
Anticipated expiration: 1989-02-15
Also published as: CH536221A; CA923814A; GB1291167A

Abstract

A rotary cutting head for severing the packaging material webs in a wrapping machine includes an elongate saw type of knife blade mounted with parallelogram linkage on one of the cutting head shafts. A face cam, coaxial with the shaft, actuates a spring biased cam follower that is connected to the knife blade. The spring(s) during each revolution of the knife blade are sequentially armed by the cam, and then triggered or released to provide an instantaneous power impulse that rapidly swings the knife blade through the web.

Description

Uite States atent Vande Castle Feb. 15, 1972 [54] ROTARY CUTTING HEAD FOR WRAPPING MACHINE [72] Inventor: Jerome J. Vande Castle Green Bay, Wis.

[73] Assignee: FMC Corporation, San Jose, Calif [22] Filed: Dec. 22, 1970 [21] Appl. No.: 5,077

[52] US. Cl ..83/322, 83/337, 83/338 [51] Int. Cl ..B26d 1/28 [58] Field ofSearch ..83/337, 338, 322;53/l82, 285

[56] References Cited UNITED STATES PATENTS 852,663 5/1907 Igou ..83/337 X 322,552 7/1885 Northrup ..83/338 X 465,427 12/1891 Cox ..83/337 1,583,393 5/1926 Coty ..83/337 2,051,453 8/1936 Mactaggart et al.. 3,057,239 10/1962 Teplitz 3,475,252 10/1969 White ..83/337 X Primary Examiner Frank T. Yost Attorney-F. W. Anderson and C. E. Tripp [5 7 1 ABSTRACT A rotary cutting head for severing the packaging material webs in a wrapping machine includes an elongate saw type of knife blade mounted with parallelogram linkage on one of the cutting head shafts. A face cam, coaxial with the shaft, actuates a spring biased cam follower that is connected to the knife blade. The spring(s) during each revolution of the knife blade are sequentially armed by the cam, and then triggered or released to provide an instantaneous power impulse that rapidly swings the knife blade through the web.

2 Claims, 10 Drawing Figures PAIENTEBFEB 15 1972 3.641.857

SHEET 1 OF 5 INVENTOR. JEROME J. VANDE CASTLE BY Jw. W

ATTORNEYS PAENTEUFEB 15 I972 3.641.857

SHEET 5 0F 5 ROTARY CUTTING HEAD FOR WRAPPING MACHINE BACKGROUND OF THE INVENTION The present field of invention is in wrapping machines, and more particularly concerns the cutoff portion of a rotary sealing and cutting head mechanism which transversely seals and severs the web material enclosing a series of articles.

Web cutoff mechanisms used for paper and foil materials in present wrapping machines include a rotary type in which a knife makes a pressure cut against the web. The knife is mounted on a rotating shaft, driven in timed relation with the web, to enable the web cutting operation to be carried out at high speed. It is usually true, however, that the service life of the knife is short because the cutting edge of the knife must press through the web against a backup or anvil member. Thus, the cutting edge should have minimal pressure against the anvil, but this is difficult to maintain in practice, and the cutting edge rapidly dulls. Another type of rotary cutoff mechanism is a shear type which effects a scissor type of cut and is more efficient than the pressure-cut mechanisms. Most shear cutoff mechanisms, though, require accurate setup adjustments and rapidly get out of adjustment during operation.

Both the pressure-cut and rotary shear cutoff mechanisms require metal to metal contact of the knife blades with cooperating parts in order to sever the web, a situation which inevitably causes more knife wear than if the knife contacts nothing but the web material. The present invention is directed to a rotary cutting head which operates in this manner, that is, the cutting edge of the web severing knife contacts only the web and has no contact whatever with any other structure.

SUMMARY OF THE INVENTION The concept of the present invention resides in Recognizing that knife blade wear results primarily from within the mechanism itself rather than from the external work it does.

. Providing a sawtooth knife blade and knife blade actuating means for arming or preloading a power mechanism which, in effect, shoots the blade diagonally endwise through the web in a combined puncturing and sliding cutting action which severs webs which are unusually difficult to cut.

. Arming and triggering the power mechanism by the normal rotary movement common to rotary web-cutoff mechanisms.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a perspective of a known type of wrapping machine incorporating the rotary cutting head of the present invention.

FIG. 2 is a diagrammatic perspective illustrating a conventional cutting and sealing head and its operation upon a tubular web enclosing spaced articles.

FIG. 3 is an isometric view ofthe cutting head of the present invention.

FIG. 4 is an enlarged isometric view of a cam and cam fol lower mechanism shown in FIG. 3.

FIG. 5 is a top plan of the FIG. 3 apparatus at reduced scale.

FIG. 6 is an enlarged section taken along lines 6-6 on FIG. 5.

FIG. 7 is an enlarged section taken along lines 7-7 on FIG. 5.

FIG. 8 is a diagrammatic transverse section viewed in the direction of web movement, and illustrates an early stage of the knife operation.

FIG. 9 is a fragmentary section of the knife structure shown in FIG. 8, and illustrates a later operational condition.

FIG. 10 is a view similar to FIG. 8, but shows the completion ofthe web severing operation.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates a known type of wrapping machine 10, the general operating principles ofwhich are disclosed in US. Pat. No. 2,546,721. In brief, the wrapping machine 10 includes a pusher type of input conveyor 12, having an upper flight that propels a single file of spaced articles A into the machine. An overhead spool 14 carries a supply of wrapping material which, in the present example, is a single thickness film web W extending under a fixed forming plow 16. The forming plow transversely curls the web downwardly around the articles and is longitudinally sealed underneath to form a tube 18, as shown in FIG. 2.

Laterally spaced conveying belts 20 (FIG. 1) grip and pull the entubed articles downstream in the direction of the arrow 21, and the web tube 18 is advanced to a rotary cutting head assembly C. A typical cutting head assembly may include upper and lower cutting head shafts 24 and 26 (FIG. 2), respectively, which straddle the web tube 18 and counterrotate in synchronism with the movement of the web.

Heated

crimping jaws

28 and 30 are mounted on the

shafts

24 and 26 to transversely heat seal the film between adjacent articles. Additionally, the gripping jaws are conventionally as sociated with web severing mechanism, not shown in FIG. 2. which severs the web to produce an output of individual packages P that are then carried from the machine, such as by a lateral discharge conveyor at 32 (FIG. I).

The present invention concerns an improved web severing mechanism 34 (FIG. 3) which is incorporated with the upper cutting head shaft 24 (FIG. I) of the cutting head assembly C. Before describing the structure of the invention, it should be noted that conventional or existing structure includes intermeshed

gears

36 and 38 on the

cutting head shafts

24 and 26 to rotate the

crimping jaws

28 and 30 in timed relation to each other and to the motion of the web. The other end of the lower shaft 26 is fixed in the frame of the wrapping machine, and the adjacent end of the upper shaft 24 is mounted in a block 40 which is mounted in a slide frame 42 (FIG. 1). Springs 44 bias the block 40 toward its operating position, and also allow upward displacement of the upper shaft 24 in the event the machine malfunctions and an article is between the crimping jaws when they close. As thus far described, the structure is known in prior art wrapping machines, except for the web severing mechanism 34.

The crimping

jaws

28 and 30 are each provided with a longitudinal central slot 35 for operating clearance of whatever web severing means are used, and the web severing mechanism of the present invention is operable within the same space limits of the slots. With continued reference to FIG. 3, the slot 35 in the upper crimping jaw 28 provides operating clearance for a saw tooth knife blade 38 which is movable between an inactive or retracted position totally concealed in the slot 35, and an active or projected position in which the cutting teeth lie outward of the edges of the slot. FIG. 3 illustrates a top dead center or intermediate position since the knife is in active position only when it is at bottom dead center, and is in a fully retracted position just prior to arriving at bottom dead center. In active position, the projecting knife blade enters the clearance slot 35 of the lower crimping jaw 30.

One convenient and inexpensive form of knife is a length of commercially available presharpened bandsaw stock. To facilitate the penetration and cutting of strong wrapping materialsin a manner later described-one side of the teeth are preferably ground so that the teeth taper, in end profile, from their apexes as shown in FIG. 6. Knife blade 38 (see also FIG. 8) is clamped between two identical knife holder arms 40, one of which is provided with threaded apertures for clamping screws 42 that pass through the other knife holder arm and through apertures in the knife blade. As best seen in FIG. 8, the knife holder arms 40 have outwardly curved end portions and are pivoted at 44 and 46, respectively, to parallelogram

links

48 and 50 so that during endwise movement of the knife holder arms 40, the knife blade teeth are maintained parallel to the axis of the cutting head shaft 24.

The parallelogram link 48 is pivotally mounted on a pivot pin 52 that is held in a mounting block 54 which is bolted to the cutting head shaft 24. In similar manner, the parallelogram link 50 is pivotally mounted on a pivot pin 56 which is held in a mounting block 58 that is bolted to the cutting head shaft 24. The latter mounting block includes a knife blade arming and triggering mechanism 60 which utilizes the rotary motion of the cutting head shaft 24 to power and release (arm and trigger) the knife blade 38.

A circular face cam 62 is bolted in rotatively adjusted position to the slide frame block 40, and functions to load a pair of compression springs 64 that arm the knife blade, and to substantially instantaneously release the springs to trigger the knife blade for its web severing function. For this purpose, the cam 62 (FIG. 4) actuates a cam follower 65 and is provided with a camming surface that has a uniform rise from a low portion 66 to a high portion 68, and an intermediate sharp dropoff or triggering portion 70.

The axial motion of the cam follower 65 along the shaft 24 actuates a T-shaped follower arm 72 which is provided with a guide shaft 74 that is slidable in the mounting block 58. A key 76 maintains the orientation of the follower arm 72 relative to the mounting block 58. A crossmember 78 of the follower arm is apertured for sliding motion over two spring guide rods 80 which each project from the flange portion ofa rod bracket 82 (FIG. 3) that is secured to the mounting block 58.

In order to transmit the motion of the follower arm 72 to the knife blade 38, the free end of the shaft 74 is provided with a pivot pin 84 connecting a pair of links 86 to the adjacent end portions of the knife blade holders 40. Due to the parallelogram link mounting for the knife blade, it will be evident that the knife blade 38 is thrust both radially and axially of the cutting head shaft 24 in a swinging motion, and that the knife blade motion occurs when the cam follower 65 drops off the high cam portion 68 to the low cam portion 66. Stated differently, the teeth of the knife blade 38 move approximately diagonally toward, through and across the plane of the web, whereby the sharp teeth easily penetrate and sever relatively strong web materials because the cutting action produces both a puncture action and a sliding cutting action. Further, the initial motion of the knife blade is more radial than axial before the parallelogram links 48 and 50 are perpendicular to the shaft 24. Therefore, the puncturing of the web is the predominant initial web-cutting action, and webs of unusual strength can readily be penetrated for the final severing action as the knife teeth move in a direction more parallel to the web. An important aspect of the knife blade action, it will be recognized, is its very rapid acceleration due to the nearly instantaneous release ofthe power impulse stored in the springs 64.

FIGS. 8-10 illustrate successive stages in arming and triggering the knife blade 38. The knife blade arming and triggering mechanism 60 (FIG. 8) is partially armed because the cam follower 65 is midway on the cam 62 at top dead center. As the cam follower moves downward over the terminal rise portion of the cam 62, it slides the follower arm 72 toward the knife blade 38 and further compresses the springs 64. At the same time, the follower arm 72 swings the parallelogram links 48 and 50 away from the cam 62, thus retracting the knife holder arms 40 radially inward so that the teeth of the knife blade 38 (FIG. 9) are concealed in the upper crimping jaw 28. Meanwhile, the heated crimping

jaws

28 and 30 have moved into heat sealing relation with the web tube 18, as shown in FIG. 2. With the web tube still gripped by the crimping jaws as shown in FIG. 10, the cam follower 65 is rapidly retracted over the triggering portion 70 of the cam 62 because at this point the armed springs 64 are free to resume their initial compression. Accordingly, the follower arm 72 is triggered to substantially instantaneously swing the knife holder arms 40 (FIG. 9) toward the cam 62, and the knife blade 38 shoots through and severs the web tube 18 with the puncturing and sliding-cut motion reviousl described. Precise adjustments II] the timing of the nrfe bla e action to the motion of the web is readily accomplished by rotatively adjusting the fixed position of the cam 62.

As previously mentioned, an important advantage of the web severing mechanism of the present invention is that the power impulse for the cutting action is derived from the stored energy of the arming springs 64, and that this energy is substantially instantaneously released to drive or shoot the knife through the web. By this means, the knife blade will easily penetrate and sever very strong web materials, including laminates which may incorporate metal foils, layers of paper and extra tough plastic films. Accordingly, a further important aspect of the present inventive concept is utilizing the rotary motion of one of the cutting head shafts for sequentially arming and triggering a power mechanism which actuates the knife blade; in contrast to presently known cam-driven web severing devices, the rotary shear of the present invention derives its effectiveness from the very rapid acceleration of the knife blade, and from the puncturing and sliding-cut mode of knife blade operation.

Although the best mode contemplated for carrying out the present invention has been herein shown and described, it will be apparent that modification and variation may be made without departing from what is regarded to be the subject matter of the invention.

I claim:

1. In a wrapping machine, a rotary cutting head comprising a rotatable driven shaft extending across a web to be severed, a fixed circular face cam coaxial with one end portion of said shaft, said cam being provided with a circular cam surface having a uniform rise with a rapid cutoff portion between the high and low points, an elongate longitudinally slotted crimping jaw mounted on said shaft, a knife blade positioned in the slot of said crimping jaw, means mounting said blade to said shaft for movement of the cutting edge of the blade into and out of said slot, and spring biased arming means mounted on said shaft adjacent one end of said knife blade and connected to said blade mounting means, said latter means including a cam follower engaged with said cam surface for loading the biasing spring during rotary movement of said shaft and said rapid cutoff portion of said cam releasing the biasing spring to provide a substantially instantaneous power impulse to said knife blade.

In a wrapping machine, a rotary cutting head comprising a rotatable driven shaft extending across a web of wrapping material to be severed, a circular face cam coaxial with one end portion of said shaft, said cam being provided with a circular cam surface having a rapid cutoff between high and low points thereof, a knife blade carried by said shaft, linkage means mounting said knife blade on said shaft for movement carrying the cutting edge of the blade radially and axially of said shaft, and cam follower means mounted on said shaft in termediate said knife blade and said face cam, said cam follower means including a follower roller engaging said cam surface and a spring urging said follower roller toward said cam surface, said cam loading said biasing spring during rotary movement of said shaft to provide stored power which is released to substantially instantaneously actuate said knife blade when said cam follower roller drops off the cutoff portion of said cam.

Claims

1. In a wrapping machine, a rotary cutting head comprising a rotatable driven shaft extending across a web to be severed, a fixed circular face cam coaxial with one end portion of said shaft, said cam being provided with a circular cam surface having a uniform rise with a rapid cutoff portion between the high and low points, an elongate longitudinally slotted crimping jaw mounted on said shaft, a knife blade positioned in the slot of said crimping jaw, means mounting said blade to said shaft for movement of the cutting edge of the blade into and out of said slot, and spring biased arming means mounted on said shaft adjacent one end of said knife blade and connected to said blade mounting means, said latter means including a cam follower engaged with said cam surface for loading the biasing spring during rotary movement of said shaft and said rapid cutoff portion of said cam releasing the biasing spring to provide a substantially instantaneous power impulse to said knife blade. hIn a wrapping machine, a rotary cutting head comprising a rotatable driven shaft extending across a web of wrapping material to be severed, a circular face cam coaxial with one end portion of said shaft, said cam being provided with a circular cam surface having a rapid cutoff between high and low points thereof, a knife blade carried by said shaft, linkage means mounting said knife blade on said shaft for movement cArrying the cutting edge of the blade radially and axially of said shaft, and cam follower means mounted on said shaft intermediate said knife blade and said face cam, said cam follower means including a follower roller engaging said cam surface and a spring urging said follower roller toward said cam surface, said cam loading said biasing spring during rotary movement of said shaft to provide stored power which is released to substantially instantaneously actuate said knife blade when said cam follower roller drops off the cutoff portion of said cam.