Patent Grant
7900657
The present invention is directed to a jaw for use in a sealless strapping machine for forming a sealless seal. More particularly, the present invention is directed to a one-piece jaw for forming a sealless seal.
Strapping machines are in widespread use. Typically, strapping machines are designed for use with metal (steel) or plastic strapping. In use, strapping is wrapped around the load, tensioned and sealed to itself. In use of metal strapping, the seal can be formed by use of a separate seal that is positioned around the strap and crimped onto the overlapping courses of strap. The seal can also be formed by gripping the strap material sections between a punch and the strapping machine jaw and cutting portions of the over- and under-lying courses of strap material into one another to interlock the strap courses. Such a seal is referred to as a sealless seal.
This action creates a locking action that provides additional strength to the strap, so that the tension in the band is maintained. The geometry of the jaw is highly engineered and does not lend itself to change. The jaws, by the nature of the design, experiences extremely high fluctuating stresses, that can result in fatigue failure if the maximum tensile stresses at the shear section exceeds half the shear yield strength. There are tremendous gains to be had if the stresses stay at or below ½ the yield strength.
Failure of the jaws can occur by fracture at the interface of the punch with the jaw structure. Again, this is due to the high localized stresses that are exhibited at this juncture. In order to address this, it has been thought that a build-up of material (e.g., making the jaw thicker) at the juncture would preclude or lessen the chances of the jaw failing. While this has increased the jaw life, it results in other undesirable characteristics, namely, the jaws have become too large and heavy and the space for the strap to move into the jaw area and for the strap to reside during the sealing operation is too small.
Another approach has been to use a two piece design that relies on improving wear performance through the use of two different materials (one for the bearing surface, e.g., the punches, and one for the bulk). Such as design lowers the shear cross sectional area that is subjected to the highest loads, and hence lowers fatigue life.
Known punches, e.g., bearing surfaces, are such as that shown in U.S. Pat. No. 6,554,030 to Cheung, et al. Each the fixed and movable punches include a plurality of punch heads. The punches are mounted to the jaw by fasteners to permit removing the punches for replacement, repair or maintenance. One drawback to this design is that the bearing surfaces (punches) are mounted to the jaw structure using fasteners, such as bolts. The bores or holes that are formed to secure the punches to the jaw structure also create areas that can be susceptible to failure.
Accordingly, there is a need for a jaw seal arrangement in which the jaw will not fail under load and that provides sufficient space in and around the punches for the positioning of strap in the jaw for sealing.
A jaw for a sealless strapping machine includes a jaw element having a body that defines a linkage portion, a hook portion and a base portion. The hook portion extends transverse to the leg portion.
The linkage portion is contiguous with the hook portion which is contiguous with the base portion. The linkage, hook and base are formed from a single piece of material.
The jaw element includes a plurality of punches, preferably three punches (three peaks with two, intermediate valleys), that extend upwardly from the base portion to defining a juncture. Each punch is defined by a peak and a valley between the peak and the peak of an adjacent punch. The juncture of the punches and the base is formed as a relieved area.
The relived area defines a first transition between the punches and the base and second transition between the base and the support leg. The first and second transitions are formed having smooth radii, defining the relieved area. The transitions are formed parallel to a longitudinal direction of the jaw.
In a present jaw, the relieved area has a depth that is about equal to or greater than a depth of a valley as measured from its respective adjacent peaks to a base of the valley. The jaw can be configure such that the peaks have about equal heights and the valleys have about equal depths.
These and other features and advantages of the present invention will be apparent from the following detailed description, in conjunction with the appended claims.
The benefits and advantages of the present invention will become more readily apparent to those of ordinary skill in the relevant art after reviewing the following detailed description and accompanying drawings, wherein:
While the present invention is susceptible of embodiment in various forms, there is shown in the drawings and will hereinafter be described a presently preferred embodiment with the understanding that the present disclosure is to be considered an exemplification of the invention and is not intended to limit the invention to the specific embodiment illustrated.
It should be further understood that the title of this section of this specification, namely, “Detailed Description Of The Invention”, relates to a requirement of the United States Patent Office, and does not imply, nor should be inferred to limit the subject matter disclosed herein.
Referring to figures, there is shown a jaw assembly 10 having a relieved region 12 embodying the principles of the present invention. The jaw assembly 10 includes a body 14 having a linkage portion 16 (that portion that is operably connected to the strapping machine—not shown), a hook portion 18 that extends generally transverse to the linkage or leg portion 16 and a base portion 20. The hook 18 extends transverse, toward an opposing hook portion (not shown).
The punches 22, which are those portions of the jaw 10 that contact and punch (deform or cut) the strap, are formed on the base portion 20 and extend upwardly from the base 20. The punches are defined by peaks 26 and valleys 28. The assembly 10 is a contiguous, unitary element. That is, unlike known jaws which use separate, attached punches, the present jaw assembly 10 uses a unitary jaw element with the punches 22 formed as part of the jaw 10. This precludes the need for holes or bores in the jaw structure (for mounting screws or bolts) that otherwise could weaken the jaw.
As best seen in
As set forth above, the punches 22 are formed as raised areas or peaks 26 (for first contact with the strap), much like teeth, and root areas or valleys 28 between the raised areas 26. The root areas 28 extend transverse to the longitudinal direction of the jaw A10 and essentially divide the peaks 26 from one another. In the illustrated embodiment, there are three peaks 26a,b,c. The peaks 26a,b,c are separated from the hook portion 18 at a transition area 30. The transition area 30 extends parallel to the direction A10 of the jaw 10 and transverse to the root areas 28. The faces of the punches (e.g., 22a and 22b) are angled slightly rearward from the peak 26 to the root 28, to define a projected or crested front face (as indicated at 23).
A present jaw 10 includes a one-piece body made of high strength high fatigue material such as high alloy steel, for example, D2 or DC53 heat treated to hardness in excess of 62 RC. Referring to FIGS. 5 and 6A-C, the jaw 10 includes a maximum possible metallic section (indicated at 32 in
The strapping surface 22 (the punch) dictates the strap strength and is formed by the peak and valley features 26, 28. A smooth radius, indicated at 34 blends in the peak 26 and valley 28 features to the back face 36 with a radius R that seamlessly blends these features of the geometry. In a present jaw 10, a sand blasted or shot blasting process is used to establish a compressive stresses at the surface of the fillet area. This improves fatigue life.
To ensure that static stresses are lowest at the shear section, the depth of the undercut d38 preferably closely matches the peak to valley height h26. This is established by thinning the section 32. To avoid any stress risers on this surface, the depth of the undercut d38 is more than or approximately equal to the peak to valley height. That is, the radius at 34 is formed to a depth d38 that is about at the valley 28 depth d28 to (relieve stresses and to) prevent failure of the jaw 10, while at the same time, retaining sufficient material to provide strength. The highest stresses are seen at the interface of the peaks 26 and the back face 36. By eliminating the point junctures (of the peaks 26 and face 36), and creating a line interface, (see at 40), the highest stress areas are eliminated.
The present jaw can be used on, for example, an M40 strapping machine currently available from ITW Signode of Glenview, Ill.
All patents referred to herein, are hereby incorporated herein by reference, whether or not specifically done so within the text of this disclosure.
In the present disclosure, the words “a” or “an” are to be taken to include both the singular and the plural. Conversely, any reference to plural items shall, where appropriate, include the singular.
From the foregoing it will be observed that numerous modifications and variations can be effectuated without departing from the true spirit and scope of the novel concepts of the present invention. It is to be understood that no limitation with respect to the specific embodiments illustrated is intended or should be inferred. The disclosure is intended to cover all such modifications as fall within the scope of the invention.
| Number | Name | Date | Kind |
|---|---|---|---|
| 2549626 | Mosey | Apr 1951 | A |
| 3284049 | Haraden | Nov 1966 | A |
| 3327619 | Sellman | Jun 1967 | A |
| 3815929 | Steinberger et al. | Jun 1974 | A |
| 4154158 | Leslie et al. | May 1979 | A |
| 4487078 | Schmitz et al. | Dec 1984 | A |
| 4546657 | Jaeger | Oct 1985 | A |
| 4781390 | Steinberger et al. | Nov 1988 | A |
| 6079303 | Lyachovitsky | Jun 2000 | A |
| 20090072502 | Weller et al. | Mar 2009 | A1 |
| Number | Date | Country |
|---|---|---|
| 2005118224 | Dec 2005 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20070277898 A1 | Dec 2007 | US |
| Number | Date | Country | |
|---|---|---|---|
| 60803408 | May 2006 | US |
