Push-type strapping seal

Abstract

 A strapping seal (1) for use in fastening together the ends of a length of strapping (9) looped around an article subsequent to tensioning. The seal (1) includes a substantially rectangular base portion (2) with flange portions (3) extending out from the long side edges thereof. The flanges (3) curve back towards each other to enclose a central space (5) adapted to receive the strapping ends. A tool is used to fasten the seal to the strapping which involves physically deforming the seal and the strapping within the seal to ensure that the strapping tension is retained and relative movement between the strapping ends within the seal is no longer possible. A gap (G) is provided between the free ends (4) of the flanges both before and after fastening.

Description

[0001] This invention relates to seals for use in fastening the two ends of a length of strapping material around a load and in particular to push-type seals for use with steel strapping which is placed under high tension around a load prior to fastening the two ends.

[0002] In order to stabilise loads (such as a coil of sheet steel or goods stacked on a pallet) for transport or storage, strapping is conventionally wound around the load and tensioned prior to the ends of the strapping being fastened together. The strapping may be a plastics or steel material and the fastening may be accomplished by welding or alternatively a seal may be applied around the two free ends of the strap and then the seal and strapping may be crimped, notched or in some other way deformed to securely lock the strap ends together.

[0003] In steel strapping applications, the seals are usually formed from a short length (up to around 60mm long) of metal having a substantially flat rectangular base section adapted to sit adjacent a surface of the strap with leg portions or flanges extending from opposite sides of the base which are adapted to wrap around the overlapped strapping ends. The seals may either be "open" or "closed". In an open seal the flanges protrude away from the base to allow the seal to be fitted over the strap after it has been tensioned and is ready for sealing. In a closed seal the flanges extend outward from the base but then curve back and overlap each other to form a flattened tubular or sleeve-like shape so that the strapping ends must be threaded into the closed seal prior to tensioning.

[0004] There are a number of known specialised types of seal which are either open or closed. Examples of the open seal types are "Snap-on" and "Open flange" while "Thread-on" and "Push-type" are examples of closed seals. Depending on the particular requirements and shape of the load, one of these different seal varieties will be used. For example, Snap-on seals are predominantly used in situations where the strapping has already been wrapped around a load and tensioned. It is then necessary to attach the seal to the tensioned strap and therefore the seal must be of the open variety and there must be room between the strap and the load to allow the seal and strap to be subsequently deformed by a suitable tool. Accordingly, Snap-on seals are effective for sealing loads having flat surfaces but are not suitable for sealing loads on non-flat surfaces such as the curved surfaces of steel coils. In comparison, as Push-type seals are slipped onto the strapping before tensioning, they may be used to join strapping around curved surfaces such as steel coils.

[0005] A suitable tool for use in tensioning strapping and then deforming the strapping and a conventional Push-type seal is described in US-A-4289175.

[0006] Existing Push-type seals suffer from occasional problems when the overlapping ends of the flanges interfere with each other during deformation thereby reducing the effectiveness of the seal. An improvement in the strength of the junction formed between the seal and strapping would be advantageous.

[0007] Accordingly, it is an object of the present invention to provide a Push-type seal which will go at least some way towards overcoming the disadvantages of prior Push-type seals.

[0008] The invention may therefore broadly be said to consist in a push-type seal for fastening together the ends of a tensioned strap which has been looped around an article, the seal adapted to be fed onto the strap in a direction parallel to the length of the strap prior to tensioning and fastening, the seal having a substantially rectangular base portion with a width marginally greater than the width of the steel strap and flange portions which extend outward from opposite side edges of the base portion and then turn back towards each other such that the flanges, together with the base portion, form a sleeve through which the strap ends may be inserted, the sleeve having a predetermined depth in a direction perpendicular to the base portion between the flanges and the base portion,
   characterised in that a gap is provided between the free ends of the flange portions wherein the width of the gap and the depth of the sleeve are such that once fed onto a strap and prior to fastening, the seal may only be removed from the strap in a direction parallel to the length of the strap.

[0009] Preferably the depth of the seal and the width of the gap between the free ends of the flanges are substantially the same.

[0010] Preferably the width of the gap between the free ends of the flange portions is between 10% to 40% of the width of the base portion.

[0011] Preferably the width of the gap between the free ends of the flange portions is about 20% of the width of the base portion.

[0012] Preferably the distance between one side edge of the base portion and the nearest point on the edge of the free end of the flange portion attached to the opposite side edge of the base portion, is less than the width of the base portion.

[0013] Preferably the distance between one side edge of the base portion and the nearest point on the edge of the free end of the flange portion attached to the opposite side edge of the base portion, is between 55% and 75% of the width of the base portion.

[0014] Preferably the distance between one side edge of the base portion and the nearest point on the edge of the free end of the flange portion attached to the opposite side edge of the base portion, is about 65% of the width of the base portion.

[0015] Preferably fastening of the strap ends together is accomplished by deformation of the seal and/or the strap in the vicinity of the seal, said deformation resulting from forces including a compressive force acting against the two side edges, a gap between the free ends of the flange portions remaining after said deformation.

[0016] The invention will now be described with reference to the accompanying drawings in which:

Figure 1 is an end elevation of the push-type seal in accordance with the present invention;

Figure 2 is a side elevation of the push-type seal of figure 1;

Figure 3 is a view from beneath the seal of Figure 1 once it has been fed onto the strapping;

Figure 4 is a view of the seal ans strapping after the seal has been fastened to the strapping;

Figure 5 is a side elevation of the fastened seal and strapping of Figure 4;

Figure 6 is a side elevation of a strap tensioning and seal fastening tool used in association with the seal of Figure 1; and

Figure 7 is a cross-sectional view of the tool of Figure 6 through the line 7-7.

[0017] With reference to the drawings and in particular Figures 1 to 5, a seal, such as a push-type seal 1, for use in fastening the two ends 7, 8 of strapping material 9 (such as plastics or more preferably steel strapping) is shown. The seal is preferably formed from a metal such as steel and is made up of a substantially rectangular base portion 2 having a predetermined width (W) and two flange portions 3. As may be seen in Figure 1, the flange portions extend outwardly from opposite side edges (the "long side" edges) of the base portion but then curve back towards each other so that the free ends 4 of the flange portions face towards each other. The base portion and flange portions together form a flattened tubular sleeve surrounding a longitudinal central region 5 having a predetermined depth (D). A gap 6 having a predetermined width (W) is provided between the free ends 4 of the flanges 3. As may be seen particularly in Figure 1, the base portion 2 may be slightly convex.

[0018] The width (W) of the seal 1 is marginally greater than the width (S) of the strapping material for which it is intended to be used. For example, the width (W) could be around 5% to 10% greater than the width of its associated strapping material. This allows the strapping to easily be fed into the longitudinal central region 5.

[0019] Because push-type seals are designed to operate under very high strapping tension, it is a required safety feature that the seal not be able to "fly off" the strapping. The dimension (Z) indicated in Figure 1 is the distance from one side edge of the base portion 2 to the free end of the flange portion attached to the opposite side edge of the base portion. The distance (Z) is the maximum width of (rigid) strapping 9 which may successfully be inserted or removed "edgeways" through the gap 6 to enter or leave the longitudinal. central region 5. An attempt to attach or detach the seal to the strapping by inserting an edge of the strapping material 9 through the gap 6 will be unsuccessful if its width is any greater than (Z). Accordingly, in contrast to some other forms of seals, notably "Snap-on" or "Open-flange" seals, the gap width (G) and the depth (D) of seal 1 are set to ensure that the seal may only be attached or detached from the strapping by relative longitudinal movement in the direction indicated by arrow 10 in Figure 3.

[0020] An estimate of the distance Z may be obtained using Pythagorus' theorem such that:

[0021] The width (W) of the seal is effectively set by the width of the available strapping (for example, 1.05*S to 1.10*S). As the dimension (Z) must be less than the strapping width (S), it is therefore possible to come up with an allowable relationship between the seal depth (D) and gap size (G) which will fulfill the requirement of exclusively longitudinal attachment and removal of the seal to the strapping.

[0022] For example, setting the depth (D) to the same distance as the width of the gap (G) provides a seal which will not allow the seal to be attached or removed from the strapping via the gap 6 (assuming that the width W is marginally greater than the strapping width S) . Preferably, the gap width (G) is influenced by external requirements and is therefore preset. As will be explained below, the size of the gap width (G) is made large enough to ensure that a small gap remains between the free ends of the flange portions after the seal has been fastened by deformation. The gap width (G) is also preferably between about 10% to about 40% of the width (W) of the base portion. This of course assumes that the depth (D) is maintained at a sufficiently small distance to maintain the overall requirement in relation to seal attachment and removal. More preferably the gap width (G) is about 20% of the width (W) of the base portion.

[0023] Preferably, the distance Z is between about 55% and 75% of the width (W) of the base portion 2. More preferably, Z is about 65% of the width (W) of the base portion 2.

[0024] In use, a length of strapping material 9 is looped around an article A (Figure 5) and the two ends of the strapping material are fed through the longitudinal central region 5 of seal 1 in the known way with the side of seal 1 including gap 6 closest to the article. One end 8 of the strapping material 9 is then bent under the seal 1 while a tool 20 (Figures 6 and 7) is used to tension the strapping by drawing the other end 7 of the strapping through the seal.

[0025] The operation of the tool 20 is conventional and more fully described in, for example, US-A-4289175 but for the present purposes it is sufficient to realise that the tool first clamps the strap end 7 between an anvil 21 and a rotatable strap tensioning feedwheel 22. An abutment member 24 of the tool is positioned between the overlapped strapping portions and abuts against one end of seal 1. The tool 20 may be pneumatically operated and includes a motor 23 which drives the feedwheel 22 thus drawing the end 7 of strapping 9 through seal 1 while the abutment member 24 is forced to push against the end of the seal which is held in place on the strapping by virtue of the bend formed near end 8 of the strapping.

[0026] Once a suitable tension has been produced in the strapping (which may be around 20kN), the motor is stopped, retaining the developed tension in the strapping, while the seal is fastened to the strapping and the excess strapping severed by shearing unit 28.

[0027] Fastening of the seal to the strapping to secure the strapping ends together is accomplished by a deformation unit 25 which engages and physically deforms the seal and the strapping within the longitudinal central region 5 of the seal. The deformation unit 25 shown in Figures 6 and 7 is a pneumatically operated jaw assembly which crimps or notches the seal. During crimping or notching, two sets of co-operating jaw members 26a, 26b and 27a, 27b engage and physically deform the side edges of the flanges 3 and also the strapping within the seal.

[0028] The jaw members form a series of short sideways cuts through the seal and also through the strapping within the seal to produce a series of "cut out" sections 11, 12, 13 and 14 which are deformed upwards, towards the tool 20 by the jaw members 27a, 27b, 26a and 26b respectively as best seen in Figures 4 and 5. It should be noted that in Figure 5, the end 8 of the strapping which should be overlying the seal has been omitted for clarity. Once fastened in the above described manner, relative movement of the ends of the strapping within the seal is prevented because the edge sections of the strapping which have been cut and deformed upwards are locked in place by the adjacent strapping edge sections which have remained in their original positions.

[0029] The jaw members also compress and thereby reduce the width (W) of the seal but it will be noted that in Figure 4, after fastening, a gap 6 remains between the free ends of the flanges 3. If the flange ends were to overlap or in some way intersect during fastening then a deterioration in the seal strength would occur as the compressive force provided by the jaw members would encounter some resistance. Because a gap remains after fastening of the seal, the strength of the seal is maximised.

[0030] It has been found that the above described seal is capable of producing joint strengths of greater than 90% of the strap strength. This is a major improvement on prior push-type seals. Furthermore, in comparison to prior push-type seals wherein the free ends of the flanges overlap, the seal according to the present invention produces a lower profile joint which is also advantageous.

Claims

1. A push-type seal for fastening together the ends of a tensioned strap which has been looped around an article, the seal adapted to be fed onto the strap in a direction parallel to the length of the strap prior to tensioning and fastening, the seal having a substantially rectangular base portion with a width marginally greater than the width of the steel strap and flange portions which extend outward from opposite side edges of the base portion and then turn back towards each other such that the flanges, together with the base portion, form a sleeve through which the strap ends may be inserted, the sleeve having a predetermined depth in a direction perpendicular to the base portion between the flanges and the base portion,
   characterised in that a gap is provided between the free ends of the flange portions wherein the width of the gap and the depth of the sleeve are such that once fed onto a strap and prior to fastening, the seal may only be removed from the strap in a direction parallel to the length of the strap.

2. A push-type seal as claimed in claim 1, wherein the depth of the seal and the width of the gap between the free ends of the flanges are substantially the same.

3. A push-type seal as claimed in claim 1 or claim 2, wherein the width of the gap between the free ends of the flange portions is between 10% to 40% of the width of the base portion.

4. A push-type seal as claimed in claim 3, wherein the width of the gap between the free ends of the flange portions is about 20% of the width of the base portion.

5. A push-Type seal as claimed in any one of the preceding claims, wherein the distance between one side edge of the base portion and the nearest point on the edge of the free end of the flange portion attached to the opposite side edge of the base portion, is less than the width of the base portion.

6. A push-type seal as claimed in any one of the preceding claims, wherein the distance between one side edge of the base portion and the nearest point on the edge of the free end of the flange portion attached to the opposite side edge of the base portion, is between 55% and 75% of the width of the base portion.

7. A push-type seal as claimed in claim 6, wherein the distance between one side edge of the base portion and the nearest point on the edge of the free end of the flange portion attached to the opposite side edge of the base portion, is about 65% of the width of the base portion.

8. A push-type seal as claimed in any one of the preceding claims, wherein fastening of the strap ends together is accomplished by deformation of the seal and/or the strap in the vicinity of the seal, said deformation resulting from forces including a compressive force acting against the two side edges, a gap between the free ends of the flange portions remaining after said deformation.

Drawing