Fastener delivery tube

Abstract: A fastener delivery tube (21) incorporates an internal guide (22) - such as a continuous sleeve lining, flexible, or resiliently deformable spring strips (34, 37, 38) or re-circulating balls (54) - forming a longitudinally movable constricton, inhibiting fastener free-fall through the tube and preserving fastener orientaton, by maintaining fastener (25) contact with a driving plunger (28) in its passage there-through and upon exit there-from into contact with a workpiece.

Description: Technical Field This invention relates to the presentation of fasteners to workpieces. More specifically, it relates to fasteners which are to be machine applied and need to be fed, through a delivery tube, from a supply, such as a carrier tape, to a remote workpiece - often with restricted access. It has been found desirable to provide such a delivery tube with the capability of exerting a controlled restraining force, sufficient to hold the fasteners in a desired orientation throughout their passage through the tube - but preferably without marking the fastener body. The term tube is used herein to embrace any configuration or disposition of chamber, enclosure or passageway. The term fastener is used herein to embrace a disparate variety of elements for joining one component to a another. Of the generality of fasteners, the invention is particularly, but not exclusively, concerned with rivets - for example hollow, tubular, self-piercing rivets, with a shank and relatively enlarged head. Fasteners, such as rivets, which are short (along their fastening axis) in relation to their girth, present special handling and delivery problems - not least because of their innate tendency to tumble, or lose their axial orientation with respect to the direction of (delivery) movement. Background Art A typical applicator for applying fasteners consists of a hydraulic cylinder carrying a fastener driving plunger mounts on a 'C' - frame. Fasteners, carried in a tape, are fed in synchronism with the cylinder operation, and are guided over the workpiece through a replaceable nozzle. Diverse mechanisms have been developed previously to ensure that machine applied fasteners arrive at the workpiece in the correct orientation (see for example EP-A-0 387 430). Where it is possible to introduce a guidance tool (as in the case of, say, spring pilot anvils, which are used to guide semi-tubular rivets into position), or where the fastener has adequate bearing surfaces along its major diameter, the guidance is generally not unduly problematic. However, where it is not possible to introduce a guidance tool and where the contact or bearing surface is limited (as for instance with a fastener with a countersunk head), or where the length of the fastener is small relative to its (head) diameter, the problems of ensuring accurate presentation are more acute. This is particularly so where the application requirements are such that the delivery tube cannot be maintained in a vertical orientation - ie absent reliance upon a gravity feed. Disclosure of Invention There is provided a delivery tube for a fastener application machine according to claim 1. The dependent claims describe preferred embodiments of the invention. It has been found that, in circumstances where it is not possible to use a guidance tool, and where the fastener has an inadequate bearing surface on its major diameter, or where the length of the fastener is small relative to its diameter, it is often advisable to restrain the fastener during its passage through the delivery tube by exerting a restraining or gripping action or force sufficient to prevent any movement of the fastener under its own weight. It has been found that the necessary restraining or gripping force can be generated by providing the delivery tube with a temporary or movable localised 'constriction'-ie a free internal diameter less than the major diameter of the fastener which is to pass through it. More particularly, by contriving that such a constriction moves longitudinally of the delivery tube, co-operatively in conjunction with fastener movement through the tube, both fastener free-fall can be restrained and a desired fastener orientation preserved. Thus, for example the delivery tube can be lined selectively with a flexible material to provide an interference fit on the major diameter of the fastener. A continuous internal sleeve provides a restraining force around the whole periphery of the fastener. However, satisfactory performance has also been achieved when the restraining force is applied by limited segments of the internal circumference of the delivery tube running longitudinally of, and parallel to axis of, the tube. Consistently successful results have been achieved by applying the restraining force with only three circumferentially-spaced, narrow, or slender, axial strips, disposed longitudinally within the tube. In each case the requirement is that the restraining force shall be adequate to hold the fastener - so that it cannot move under its own weight and will retain its position within the delivery tube regardless of the orientation of the delivery tube, until it is propelled along the tube by a plunger. According to one aspect of the invention there is provided a delivery tube for a fastener application machine, for transferring fasteners with a shank and relatively enlarged head, discretely in succession, from a supply, such as a carrier tape, to a fastening station, at which fasteners are applied to a workpiece, by a driving head of a fastener application plunger; movable internally of the delivery tube, the delivery tube incorporating a guide, to bear upon a fastener in its transit through the delivery tube, by forming a local passage constriction, movable longitudinally of the tube, co-operatively in conjunction with fastener movement, to restrain the fastener head from free-fall there-through, and preserve a desired fastener orientation within the guide. Thus the guide may comprise a continuous internal sleeve lining. Alternatively, the guide may comprise a plurality of longitudinally-extending guide elements, co-operatively disposed in a circumferentially-spaced array, to bear continuously upon a fastener, in its transit through the guide. In yet another variant, the guide comprises a plurality of circumferentially-spaced, flexible or resiliently-deformable, inwardly-intruding strips. One particular guide configuration relies upon an array of three symmetrically-disposed guide members. The invention embraces a delivery tube of the kind set out above, co-operatively disposed with a fastener carrier tape, incorporating a plurality of individual fastener retention holes, each with a profiled periphery, to produce a predetermined mode of tape deformation, for controlled fastener discharge, through depending tape flaps, directed into a funnel shaped array, to lie co-operatively within the mouth of the delivery tube, and thereby to preserve a desired fastener orientation, upon controlled discharge from the tape and tube entry. The invention also embraces a fastener installation machine incorporating a fastener delivery tube as set out above. There now follows a description of some particular embodiments of the invention, by way of example only, with reference to the accompanying diagrammatic and schematic drawings, in which: Description of Drawings Figure 1 shows the general overall configuration of a typical applicator and highlights the position of the delivery tube; Figure 2 shows a section of a typical delivery tube lined with a flexible material with a fastener held partially along the tube; Figure 3 shows a plan view of the delivery tube of Figure 2; and Figures 4 and 5 show vertical views of alternative delivery tube linings to that of Figure 2. Referring to the drawings, and in particular Figure 1, a fastener applicator 20 has a fluid-actuated ram 31, with a movable piston or plunger driving head 28 for contacting the head of an individual fastener 25 and driving the fastener 25 into a workpiece (not shown) mounted in the throat 33 of a C-frame 32. For repetitive operation, fasteners 25 are transported to the driving plunger 28 as a linear succession in a carrier tape 26, typically of flexible synthetic plastics, from a reservoir or supply spool or cartridge 29 to a position underneath the driving plunger 28. In order to gain access to a workpiece in positions where space is restricted, it is often necessary to release a fastener 25 from the carrier tape at a point remote from the workpiece and to use a delivery tube 21 to convey the fastener 25 to the point of application. It is with such a delivery tube 21 - and the interaction of its internal passage with the external profile of a fastener 25 - that the present invention is particularly concerned. More specifically, In their passage down the delivery tube 21, the fasteners 25 can lose contact with the plunger driving head 28 and become disorientated, or mis-aligned, so that when the workpiece is contacted upon their emergence from the delivery tube 21, they are installed mis-aligned or indeed not properly secured at all. Fasteners posing particular problem are those whose length is short compared with their girth, since they exhibit no natural self-alignment, as with a relatively long thin fastener. Short fasteners, especially short, self-piercing tubular rivets with a shank 24 and relatively enlarged head 27 are advantageous for fastening in shallow depth materials to achieve a satisfactory joint, but exhibit a natural tendency to tumble when passed through a delivery tube. In order to combat this effect, Figures 2 and 3 show the provision of a simple, continuous tubular lining 22 - of resiliently deformable material - within the delivery tube 21 to restrain an individual fastener 25 from free-fall down the tube internal passage 23 - whose cross-section is thus constricted thereby. This restraint is sufficient to preserve contact between the downwardly moving driving head 28 and the head 27 of a fastener 25. It has been found unnecessary for the lining 22 to be continuous around the inner circumference of the passage 23 and Figure 4 shows three equi-angularly spaced inwardly projecting ribs 34 on a common sleeve 35. Figure 5 depicts another intermittent profile for a sleeve lining 36. The lining 22 could be reduced to slender strips.

Claims: A delivery tube (21) for a fastener application machine (20) for delivering fasteners (25) in succession to a fastening station at which the fasteners are applied to a workpiece, the fasteners each having an elongate shank (24) and a relatively enlarged head (27) having a predetermined cross-sectional dimension, and the application machine having a fastener application plunger (28); the delivery tube (21) comprising: a tubular member provided with an internal longitudinal passage with an internal cross-sectional dimension greater than the predetermined cross-sectional dimension of the enlarged head (27) of the fastener (25) when the shank (24) is substantially aligned with the longitudinal direction of said passage, and displaceable guide means along and within the internal surface of the tubular member, for rendering the cross-sectional dimension smaller than said predetermined cross-sectional dimension of said enlarged head, the guide means being axially continuous and being longitudinally arranged along the length of the tubular member, characterised in that the guide means comprises a lining (22) of the passage, the lining being made of resiliently deformable material, which lining forms a local passage constriction resulting from an interference fit with the enlarged head (27) of the fastener, which local passage constriction is longitudinally movable along the delivery tube as the fastener is propelled along the tube by the plunger (28), such that the guide means restrains the fastener head from free-fall throughout its passage through the delivery tube until the fastener reaches the point of application regardless of the orientation of the delivery tube and preserves a desired fastener orientation while enabling the fastener (25) to advance and be guided along the delivery tube (21) towards the workpiece. A delivery tube (21) as defined in claim 1, wherein said lining comprises a plurality of longitudinally extending guide elements disposed in a circumferentially-spaced array about said internal surface. A delivery tube (21) as defined in claim 2, wherein said guide elements comprise inwardly projecting ribs (34) formed on an internal tubular sleeve (35).

Inventors: EDWARDS CYRIL KENNETH, EDWARDS, CYRIL KENNETH
Applicants: ARIEL IND PLC, ARIEL INDUSTRIES PLC
Application year: 1993
Main classification: B21J15
IPC codes: A44B19, B21J15, B65G47, B23P19, B25B23