Method and apparatus for gripping a bonding strap

Abstract: In a strap binding machine the grip means to hold a free end portion of the strap (3) whilst it is tensioned and bonded to itself includes a jaw (6) and a stationary part of a cutter (5). These parts include intermeshing projections (5A′, 6A′) which form the free end portion of the strap into a serpentine shape with a number of concave and convex portions (U,V).

Description: The present invention relates to improvements in a method and apparatus for securing and gripping a preceding portion of a strap such as steel band which is wound around an article to be bound and then tightened before its ends are bonded together. In the past the preceding portion of the strap has been gripped between a pair of jaws as will be described in detail subsequently with reference to the accompanying drawings. The jaws may grip the strap at a single point or may include at least one serrated jaw to improve the grip between them and the strap. In both cases the surface of the strap tends to be scored by the jaws which can lead to weakening and failure of the strapping. According to a first aspect of this invention a method of gripping a strap whilst bonding its ends together including the steps of: winding a binding strap around articles to be bound, gripping to secure and hold a preceding portion of the strap, taking up the succeeding portion of the strap, and bonding overlapping strap portions of the preceding portion and the succeeding portion to each other whilst applying tension to them; is characterised in that the preceding portion of the strap is gripped by grip means including a jaw and a stationary cutter which include intermeshing projections which form the preceding portion of the strap into a serpentine shape with a number of concave and convex portions. According to a second aspect of this invention a strap binding machine includes a binding head including grip means to hold a preceding portion of the strap, tensioning means to apply tension to a succeeding portion of the strap after it has been wrapped around an article to be bound, bonding means to bond the preceding portion and succeeding portion of the strap together, and a cutter to sever the succeeding portion of the strap after it is bonded, and is characterised in that the grip means is formed by a jaw and stationary part of the cutter and in which these include intermeshing projections which form the preceding portion of the strap into a serpentine shape with a number of concave and convex portions. A particular example of a method and apparatus in accordance with this invention will now be described and contrasted with the prior art with reference to the accompanying drawings; in which:- Figure 1 is a side elevation of a bonded strap; Figure 2 is a plan of the bonded strap; Figure 3 is a side elevation drawn to a larger scale of the grip and cutter of the binding head; Figure 4 is a plan of the strap illustrating the grip marks formed on it; Figure 5 is a schematic view illustrating the strap binding maching; Figure 6(a) is a partly sectioned side elevation of a first conventional binding head; Figure 6(b) is a partly sectioned elevation of a second conventional binding head; Figure 7(a) is a plan of the score marks formed by the first conventional binding head; and, Figure 7(b) is a plan of multiple score marks formed by the second conventional binding head. A conventional strap binding method will be described with reference to Figures 5 to 7. A binding apparatus has a multi-functional binding head 1, to be discussed later, which is vertically movable with respect to its frame. Articles 2 to be bound are fed to a predetermined position under the binding head 1 in the frame. A binding strap 3 such as a steel band is fed from a dispenser by the forward rotation of reversible rollers 4 of the binding head 1. The strap 3 is guided around articles to be bound 2 through a chute and gate (not shown). After making a round of the articles to be bound, the preceding portion 3a of the strap 3 is returned to the binding head 1. When the preceding portion 3a of the strap 3 comes under the succeeding portion 3b of the strap 3 as shown in Figure 6(a), a stationary cutter 5 and a jaw 6 of the binding head 1 are closed to grip a portion of the preceding portion 3a, so that the grip portion of the preceding portion 3a is held and secured. With the preceding portion fo the strap gripped, the drive rollers 4 are reversely rotated, thereby to take up the succeeding portion 3b. This causes the winding strap 3 to come off the chute and the gate such that the articles 2 to be bound are wound tightly with the strap 3. At the same time, the binding head 1 is lowered onto the articles to be bound, as shown by an arrow d . While a high tension is being applied to the winding strap 3 by the strong reverse rotation of the drive rollers 4, a C-sectioned seal fitment 7, for example, is placed on the overlapping strap portions of the preceding portion 3a and the succeeding portion 3b, and the seal fitment is turned and crimped at its lateral edges. The lateral edges are partially notched by the jaw 6 and notchers 9 which are lowered. This forms notches 10 which are turned in opposite directions to clamp them together to bond the overlapping strap portions together. At the same time, the bonded strap portion is cut and separated from the rearwardly connecting strap portion 3c, by and between the stationary cutter 5 and a movable cutter 11 which is lowered. When the jaw 6 serving as an underlay is transversely pulled out, the bonded strap is resiliently returned by the amount of looseness generated by the removal of the jaw 6. However, a sufficiently high tension still remains in the binding strap to assure a good binding effect. In the foregoing, the most common conventional strap binding method has been described. However a number of different bonding means may be used. For example, the overlapping strap portions may be bonded to each other by spot welding. Further, the grip means may also have a variety of forms. Besides the single-type grip means as shown in Figure 6a a multi-grip means is also known as shown in Figure 6b. In this the strap is gripped by and between a sawtooth holding surface 5S formed on the stationary cutter 5 and the flat surface of the jaw 6. Regardless of the types of the grip means and the bonding means used the following series of steps are carried out: winding the strap 3; gripping the preceding portion 3a; taking up and winding the succeeding portion 3b; tightening and tensioning the strap; bonding the preceding portion 3a and the succeeding portion 3b to each other under tension; cutting and separating the bonded strap from the connecting portion 3c; and removing the underlay. By and between the stationary cutter 5 and the jaw 6, the strap preceding portion 3a should be gripped as tightly as possible and held in order to resist the high tension applied to the succeeding strap portion 3b by the drive rollers 4. Even after the strap succeeding portion 3c has been separated from the strap connecting portion 3c, a high tension still exists between the gripped portion and the seal fitment bonding portion. A steel-band strap having strength capable of sufficiently resisting these tensions is typically used. For example, there may be used a steel-band strap having a width of 3/4 to 1 1/4 inch (19 to 32 mm), a thickness of 1 mm or less, and a resistance to tension of about 75 to 100 kgs/mm². However, the strong gripping above-mentioned produces scores or grip marks as grip traces on the strap preceding portion 3a at the gripped portions. Further, these gripped portions are normally bent to some extent. Figure 7(a) shows a grip mark 12s produced in the case of the single grip device shown in Figure 6a, while Figure 7(b) shows grip marks 12m produced in the case of the multiple grip device shown in Figure 6b. If the gripping force is smaller than the tightening tension applied to the strap, the strap may be cut or slip at the gripped portions, and the binding residual tension is considerably reduced. The main problems encountered in the single grip are set forth below. (I) The single grip mark 12S is relatively large and deep. Accordingly, if an excessive tension is applied to the winding strap to enhance the binding force, the strap may break at the scored portion. (II) The scored portion of the strap is apt to cause slip, decreasing the tension remaining after the strap end portions have been bonded to each other. (III) Since the scar of grip mark is great, there is a possibility of the strap being broken, if a binding force or an external force in the shearing direction is applied to the binding strap during transport of the bound articles. The main problems encountered in the multiple grips are set forth below. (I) The gripped portions are extended in the strap longitudinal direction. Accordingly, the distance between the strap gripped portions and the strap end portion bonded with the seal fitment or the like is increased. This increases the looseness generated after strap bonding, so that the drop in residual tension is increased. Thus, the multiple gripping is not suitable for binding coil-like or small-size articles, since the influence of such drop is considerable. (II) It is required that for the multiple grip to be effective that a number of grip points are arranged equidistant from the jaw and the grip conditions are equilized along the length. Accordingly, no free space is provided in the thickness direction of the binding strap. This requires a fine adjustment for the strap portion to be held effectively. (III) The bonding members of the binding head are increased in size, causing the head to be large-sized. In accordance with the present invention the grip means includes a jaw and a staionary cutter of the binding head formed with intermeshing projections so that the strap is formed into a serpentine shape with a plurality of concave and convex portions. Figures 1 and 3 illustrate the present invention. The preceding portion 3a of the winding strap 3 is gripped and held between and by the lower jaw 6A and an upper stationary cutter 5A, while the strap 3 is formed into a serpentine shape by being pushed up at first positions thereof in a direction shown by arrows U and pushed down at second positions in a direction shown by arrows V. The first positions alternate with the second positions. With tension applied to the strap between the gripped portions and the portion tightened by the drive rollers, a seal fitment 7 is placed on the overlapping strap portions of the preceding portion 3a and the succeeding portion 3b. Notches 10 are then formed to bond the overlapping strap portions to each other. The strap portion thus bonded is cut and separated from the strap connecting portion at a cut end 3e with a movable cutter 11A. As shown in a plan view of Fgiure 2, grip marks are formed on the strap at its portion near the centre so that a plurality of convex marks 12U and concave marks 12V are respectively formed on the obverse and reverse surfaces of the strap in an adjacent manner. The method of the present invention provides the following operations and effects. (I) The strap preceding portion is gripped at positions on the obverse and reverse surfaces thereof, these obverse and reverse positions alternating with each other in the strap longitudinal direction. This eliminates a fine adjustment of the intermeshing tips with respect to the thickness of the strap. (II) The double-wave gripping substantially prevents the gripped portions from slipping due to tension applied to the strap. (III) The wave-shape gripping causes the grip marks to be convex and concave, thus producing no scars which produce a cutting or scoring effect. Accordingly, the surface of the strap is hardly damaged. (IV) It is not required to grip the strap at as many points as required in the conventional method. Accordingly, a spread of the gripped portions is small and equal to that in the single grip according to the conventional method. This eliminates the need of large-sized grip means. Accordingly, the drop in strap residual tension is reduced. (V) The wave-like gripping increases the grip resistance against the strap tension. It is therefore possible to resist the strap tension by merely gripping the centre band area of the strap. Accordingly, both lateral edges of the strap are preserved intact. (VI) The grip marks are in the form of a wave. Accordingly the binding strap is hardly scored even though an external force is applied during transportation. The following description will discuss in more detail an example of the present invention with reference to Figures 3 and 4. The gripping method in accordance with the present invention includes the same steps as those in the conventional method, of: winding a binding strap around articles to be bound, by a binding head; and gripping, while securing and holding, the grip portions of the preceding portion of the strap returned to the binding head. Figure 3 is a vertical section view in side elevation of an example of the grip means used in the gripping method of the present invention. Figure 3 shows the relative positions of the stationary cutter 5A and the jaw 6A in a closed position. The jaw 6A is provided on the intermeshing jaw surface thereof with a plurality of convex portion 6A' and concave portions 6A''. The stationary cutter 5A is provided on the intermeshing jaw surface thereof with a concave portion 5a'' and convex portions 5A'. The convex portions 6A' are opposite to the concave portion 5A'', while the concave portions 6A'' are opposite to the convex portions 5A'. Figure 4 shows, in plan, the grip marks formed on the strap preceding portions 3a by the grip means according to the method of the present invention. The grip marks include convex marks 12U and concave marks 12V which are formed, at a central area of the strap, alternately in the longitudinal direction thereof. Figure 3 also shows a movable cutter 11A, and the cut end 3e at which the strap succeeding portion 3b is cut and separated from the connecting portion of the strap stock. According to the present invention, when bonding the end portions of a strap wound on articles to be bound, the preceding portion of the strap is securely gripped to resist the tension applied to the strap at the time when the strap is tightened and when the strap end portions are subsequently bonded to each other. Convex and concave grip marks are formed in the vicinity of one another. This reduces the drop in strap tension remaining after the strap end portions have been bonded to each other. Accordingly, the binding strap is hardly scored assuring a good binding.

Claims: A method of gripping a strap (3) whilst bonding its ends together including the steps of: winding a binding strap around articles (2) to be bound, gripping to secure and hold a preceding portion (3a) of the strap, taking up the succeeding portion (3b) of the strap, and bonding overlapping strap portions of the preceding portion and the succeeding portion to each other whilst applying tension to them; characterised in that the preceding portion of the strap is gripped by grip means including a jaw (6) and a stationary cutter (5) which include intermeshing projections (5A', 6A') which form the preceding portion of the strap into a serpentine shape with a number of concave and convex portions. A strap binding machine includes a binding head (1) including grip means (5, 6) to hold a preceding portion (3a) of the strap (3), tensioning means (4) to apply tension to a succeeding portion (3b) of the strap (3) after it has been wrapped around an article (2) to be bound, bonding means (9) to bond the preceding portion (3a) and succeeding portion (3b) of the strap together, and a cutter (5, 11) to sever the succeeding portion (3b) of the strap after its bond, characterised in that the grip means is formed by a jaw (6) and stationary part (5) of the cutter and in which these include intermeshing projections (5A', 6A') which form the preceding portion of the strap (3a) into a serpentine shape with a number of concave and convex portions.

Inventors: KATO KANAMI, KATO, KANAMI
Applicants: SIGNODE KK, SIGNODE KABUSHIKI KAISHA
Application year: 1989
Main classification: B65B13
IPC codes: B65B13