Adhesive block
United States Patent 3917123
The invention concerns an adhesive block of hot-melting material for an adhesive dispenser in which the block advances along a feed passage under the action of pressurised fluid, is melted and is dispensed as a liquid adhesive, the block having one or more flanges formed on its body, the or each flange being shaped and dimensioned to be capable of serving as a piston face for the direct application of pressurised fluid thereto, whereby the block can be advanced along the feed passage in sealing engagement therewith. Processes for forming such a block are described, including a cold forming process. A variety of block-and-flange configuration are disclosed.
US Patent References:
Machine for melting and feeding solidified materials
Czarnecki - December 1956 - 2773496
Self sealing piston
De John - July 1961 - 2992052
Dispenser for materials under pressure
Abplanalp - November 1965 - 3217936
Separating medium for use in pressurized dispensing containers
Towns - May 1968 - 3381863
COLLAPSIBLE TUBE AND FOLLOWER
Ballin - February 1970 - 3493147
Machine for melting and feeding solidified materials
Czarnecki - December 1956 - 2773496
Self sealing piston
De John - July 1961 - 2992052
Dispenser for materials under pressure
Abplanalp - November 1965 - 3217936
Separating medium for use in pressurized dispensing containers
Towns - May 1968 - 3381863
COLLAPSIBLE TUBE AND FOLLOWER
Ballin - February 1970 - 3493147
Application Number:
05/452381
Publication Date:
11/04/1975
Filing Date:
03/18/1974
View Patent Images:
Export Citation:
Assignee:
Sale Tilney AG (Zug, CH)
Primary Class:
Other Classes:
222/394, 156/578, 222/325
International Classes:
C09J5/00; C09H11/00
Field of Search:
222/389,386.5,325,146HE,394 161/179 401/1 156/578
Primary Examiner:
Tollberg, Stanley H.
Assistant Examiner:
Shannon, John P.
Attorney, Agent or Firm:
Stowell, Harold L.
Claims:
I claim as my invention
1. A solid adhesive block made of hot-melting material for use in an adhesive dispenser of the kind including a feed passage, a dispensing outlet for dispensing adhesive in substantially liquid form, means for supplying pressurised fluid for advancing the block along the feed passage towards the dispensing outlet, and means for melting a part of the block before it reaches said outlet, wherein the improvement in said adhesive block comprises:
2. An adhesive block according to claim 1 wherein the block has a plurality of said flanges spaced apart along its length to form a plurality of said seals.
3. An adhesive block according to claim 1 wherein said recess is an endless groove of substantially V-shaped cross-section.
4. An adhesive block according to claim 1 wherein the outer and inner surfaces of the flange are convergent in the rearward direction.
5. An adhesive block according to claim 1 wherein the outer and inner surface of the flange are convergent in the forward direction.
6. An adhesive block according to claim 2 wherein the said flanges are mutually parallel, equispaced, each flange being of the shape of a substantially closed ring, the said flanges being formed by pressure forming.
7. A solid adhesive block made of hot-melting material for use in an adhesive dispenser of the kind including a feed passage, a dispensing outlet for dispensing adhesive in substantially liquid form, means for supplying pressurised fluid for advancing the block along the feed passage towards the dispensing outlet, and means for melting a part of the block before it reaches said outlet, wherein the improvement in said adhesive block comprises:
8. An adhesive block according to claim 7 wherein the said flanges are mutually parallel, equispaced, similarly shaped and sized, and are formed by turning.
9. An adhesive block according to claim 7 wherein the said flanges are mutually parallel, equispaced, each flange being of the shape of a substantially closed ring, the said flanges being formed by rolling.
1. A solid adhesive block made of hot-melting material for use in an adhesive dispenser of the kind including a feed passage, a dispensing outlet for dispensing adhesive in substantially liquid form, means for supplying pressurised fluid for advancing the block along the feed passage towards the dispensing outlet, and means for melting a part of the block before it reaches said outlet, wherein the improvement in said adhesive block comprises:
2. An adhesive block according to claim 1 wherein the block has a plurality of said flanges spaced apart along its length to form a plurality of said seals.
3. An adhesive block according to claim 1 wherein said recess is an endless groove of substantially V-shaped cross-section.
4. An adhesive block according to claim 1 wherein the outer and inner surfaces of the flange are convergent in the rearward direction.
5. An adhesive block according to claim 1 wherein the outer and inner surface of the flange are convergent in the forward direction.
6. An adhesive block according to claim 2 wherein the said flanges are mutually parallel, equispaced, each flange being of the shape of a substantially closed ring, the said flanges being formed by pressure forming.
7. A solid adhesive block made of hot-melting material for use in an adhesive dispenser of the kind including a feed passage, a dispensing outlet for dispensing adhesive in substantially liquid form, means for supplying pressurised fluid for advancing the block along the feed passage towards the dispensing outlet, and means for melting a part of the block before it reaches said outlet, wherein the improvement in said adhesive block comprises:
8. An adhesive block according to claim 7 wherein the said flanges are mutually parallel, equispaced, similarly shaped and sized, and are formed by turning.
9. An adhesive block according to claim 7 wherein the said flanges are mutually parallel, equispaced, each flange being of the shape of a substantially closed ring, the said flanges being formed by rolling.
Description:
The invention relates to a solid adhesive block and a process for making it, for use in hot-melt adhesive dispensing devices, and is an improvement in or modification of U.S. Pat. No. 429,150 filed on Dec. 28, 1973 by Robert T. Allsop. The invention disclosed in said application will hereinafter be referred to as "the Allsop invention".
It is known to apply adhesive to a workpiece by means of a dispensing device which has a feed passage charged with an elongated mass of adhesive which at room temperature is non-liquid, substantially non-tacky, and substantially shape-retaining; the device includes means for melting a part of the adhesive block, a dispensing outlet for dispensing adhesive in substantially liquid form, and means for supplying pressurised fluid for advancing the adhesive block along the feed passage towards the dispensing outlet. Such a dispensing device will hereinafter be referred to as "an adhesive dispenser of the type defined".
The Allsop invention sought to simplify the design of the adhesive mass, enabling in turn the mechanical construction of the dispenser to be simplified by obviating the need for a piston which was employed in prior art dispensers to propel the adhesive block. Accordingly, the Allsop invention disclosed and claimed a solid adhesive member made of hot-melting material for use in an adhesive dispenser which dispenser includes a feed passage, means for melting a part of the adhesive member, a dispensing outlet for dispensing adhesive in substantially liquid form, and means for supplying pressurised fluid for advancing the adhesive member along the feed passage towards the dispensing outlet, wherein the adhesive member is formed at or adjacent the rear end thereof, (relative to the direction of its advance in use) with a flange shaped and dimensioned so as to be capable of being advanced along the feed passage in substantially fluid-tight sealing engagement therewith, said rear end, including the flange, serving in use as a piston face for the direct application of pressurised fluid thereto.
In a preferred embodiment of the Allsop invention, the rear end of the adhesive block is concave or includes a recess, cavity or other opening. This has the advantage that application of fluid pressure to the rear end will cause pressure to be exerted not only in the axial, i.e. advancing direction, but also peripherally against the flange, whereby to help maintain the latter in satisfactory sealing relationship with the internal bore of the feeding passage.
While this invention has the same broad aims as the Allsop invention, viz. the simplification of the design of the dispensing device by obviating the need for a piston, this invention has the additional aims of providing varying configurations of the block and flange or flanges; improving the quality of the seal between the adhesive block and the feed passage; and improving the resilience of the seal-forming flange or flanges formed on the adhesive block. Further aims of the invention include the provision of a plurality of processes for manufacturing the adhesive block. In one preferred process, the flange(s) may be formed after the block has been moulded and trimmed to size, and wherein the configuration of the seal-forming rear end may be varied.
According therefore to one exemplary aspect of this invention, there is provided a solid adhesive block made of hot-melting melting material for use in an adhesive dispenser of the type defined, wherein the end of the adhesive block which, relative to the direction of its advance in use, is the rear end, is provided with a peripheral flange shaped and dimensioned so as to constitute a resilient, rearwardly and outwardly projecting sealing portion, the latter being separated from the central portion by a recess, whereby in use the direct application of pressurised fluid to said rear end will cause the block to be advanced along the feed passage with the flange in resilient yet fluid-tight sealing engagement therewith.
A portable adhesive dispensing device in the form of a trigger-actuated gun is known wherein the gun has a barrel portion containing said feed passage of a length sufficient to accommodate at least one adhesive block and the remainder of another previously already used block placed end-to-end. Actuation of the trigger causes compressed air to be applied to the rearmost block by way of a piston.
It is also often found that on loading the barrel an air lock may form between the front end of the rear adhesive block and the rear end of the front adhesive block or block part. Such an air lock is obviously undesirable from the viewpoint of continuous and uniform dispensing of adhesive. Moreover, when the uncovered end of a block is place adjacent the piston, some undesired adhesion between the block and the piston may occur.
Bearing in mind that such guns are frequently operated by relatively unskilled personnel, certain preferred embodiments of this invention seek to eliminate the above-mentioned disadvantages by virtue of the fact that the different shapes of the front and rear ends of the adhesive block will enable an operator to distinguish between said ends and to load the gun correctly, and by obviating the need for a piston.
Preferably, the adhesive block is a one-piece cylindrical member with a substantially planar front end and a substantially planar rear end or central portion, said flange being annular.
Advantageously, said recess may be a groove of substantially V-shaped cross-section.
In one optional embodiment, the radially inner and radially outer surface of the annular flange are forwardly or rearwardly convergant. Preferably, the flange and the central portion of the rear end terminate in the same transverse plane.
According to another exemplary aspect of the invention, there is provided a process for making a solid adhesive block as set forth above, the process comprising providing a mould having a bevelled wall portion, disposing an adhesive block in the mould so that one end of the block is located adjacent the said bevelled wall portion, deforming the periphery of said one end of the block against the said bevelled wall portion and cutting a recess in said end so as to form an outwardly extending peripheral flange separated by a recess from the central portion of said one end.
Preferably the deforming and cutting steps are carried out by a bevelled forming tool.
The angel of bevelling of the forming tool may be the same as, or may be smaller than, that of the bevelled mould wall portion; in the latter case, the flange produced thereby will have a feathered edge.
According to yet another aspect of the invention, there is provided a solid adhesive block made of hot-melting material for use in an adhesive dispenser of the type defined, wherein the block is provided with a plurality of spaced apart flanges along its length, each flange being capable of forming a resiliently yielding seal with the internal bore of the dispenser. The flanges may be substantially ring-shaped and formed by a process akin to cold-rolling or pressure-forming. Alternatively, they may project rearwardly with feathered edges, produces by turning involving a plough-shaped cutting tool. The presence of a plurality of seals obviously improves the overall quality of the seal between the block and the bore in the dispenser.
Alternative preferred embodiments of the invention seek to provide adhesive blocks which are capable of being inserted into a dispensing gun in either longitudinal orientation, the blocks having a plurality of featherededge seals, with some feathered edges "pointing" forwardly (in relation to the direction of advance of the block in use) and others pointing rearwardly.
The invention also includes in its scope apparatus for carrying out the processes set forth above, and also products made by said processes and by said apparatus.
The hot-melt adhesive is well-known as such and may, for example, be made of a polyamide resin or a polyester resin or an ethyl-vinyl-acetate (EVA) resin, or of any suitable mixture of these. The adhesive may incorporate wax(es), filler(s), or extender(s) and additives to influence the viscosity, melting point or other physical property of the adhesive block.
The invention is illustrated, by way of example only, with reference to the accompanying purely schematic drawings, wherein
FIGS. 1 to 3 are respective sectional views of successive stages of a pressure-forming process for making an adhesive block, according to the present invention,
FIGS. 4 and 5 show an adhesive block, respectively in elevation and in section, before the process is carried out, i.e. before the block is placed in the mould case shown in FIG. 1,
FIGS. 5 to 8 illustrate, respectively in elevation and in two mutually normal cross-sections an adhesive block according to the invention and made by the process shown in FIGS. 1 to 3, FIG. 8 being a section along line A--A in FIG. 7,
FIGS. 9 and 10 respectively illustrate a variant of the forming tool shown in FIGS. 1 to 3, whereby adhesive blocks according to the invention may be fabricated with a sealing portion having a feathered edge, and
FIGS. 11 and 12 respectively illustrate variants of the adhesive block, FIG. 11 showing a variant formed by a turning process e.g. on a lathe, while FIG. 12 shows a variant formed by cold-rolling.
Referring first to FIGS. 1 to 3, a pressure-forming process for making a hot-melt adhesive block according to the invention is illustrated. From the resin material an elongated, substantially cylindrical body 40 is made by a previous moulding process. The ends 41 and 42 of the body are planar and transverse to the central longitudinal axis 43 of the body 40. The body 40 is then placed (FIG. 1) in an annular mould case 44 which may or may not be the same as was used to mould the body 40.
The mould case 44 has a cylindrical outer surface. One end of the inner surface 45 is, however, chamfered or bevelled as shown at 46. The angle of bevelling is predetermined.
The mould case 44 is arranged to cooperate with a forming fool 50 which is displaceable, by any suitable means not shown, along the axis 43 towards and away from the mould case 44. The tool 50 may, if desired, be additionally rotatable about that axis. It has a frusto-conical end 51, the cone angle of which is substantially identical with the angle of bevelling of the part 46 of the inner surface 45 of the mould case 44. As shown by chain lines, the forming tool 50 has a cylindrical recess 52 extending from the bottom of the frusto-conical end 51. The cylindrical external surface 53 of the forming tool has a diameter which is equal to or greater than the diameter of the inner surface 45 of the moulding case 44, but is smaller than the maximum diameter of the bevelled part 46.
As shown by the sequence in FIGS. 1 to 3, when the forming tool 50 is pressed into the body 40 along the arrow 55, and then withdrawn, the end 42 of the body 40 will be cut and deformed into the configuration best appreciated from FIG. 8. In other words, an annular recess or groove 56 of V-shaped cross-section is cut in the end 42 which groove separates an unaltered central portion 57 from a peripheral portion or flange 58. The flange 58 is shaped by deformation between the part 46 and the frusto-conical end 51 and can be seen to be an outwardly and upwardly flaring annular flange with substantially parallel radially inner and outer surfaces.
FIGS. 4 and 5 on the one hand, and FIGS. 6 to 8 on the other hand, respectively illustrate the body 40 before and after the process shown in FIGS. 1 to 3 has been carried out.
In use, the flanged body 40 may be fed into a piston-less fluid pressure operated portable adhesive dispenser. The body 40 is loaded with the plain end 11 as the front end, while the end 42 with the flange 58 will be the rear end, the flange and the central portion 57 together constituting a piston face for the direct application of fluid pressure thereto. The dimensions of the mould case and of the forming tool are so chosen that the maximum outer diameter of the flange 58 is somewhat greater than the diameter of the feed passage in the dispenser. By virtue of the resilience and shape of the flange 58, it will in use be in fluid-tight, sealing yet yielding engagement with the wall of the feed passage so that the body or block may advance therealong under the action of the applied fluid pressure.
The presence of the groove 56 of V-shaped cross-section has two important functions. Firstly, it assists in imparting resilience to the flange 58. Secondly, in use, the application of fluid pressure to the rear end 42 will cause pressure to be exerted within the groove 56 with a radially outward component which helps to maintain the flange in sealing engagement with the feed passage.
It will be appreciated that by varying the cone angle of the forming tool and the cooperating angle of bevelling in the mould case, the shape of the flange 58 may be varied.
FIGS. 9 and 10 illustrate variants of the forming tool 50, the differences being in the respective cone angles of the respective frusto-conical ends 51a and 51b. By varying the cone angle in this way, but maintaining the angle of bevelling of the part 46 of the mould case 44, the resulting flange 58 will have a feathered edge, respectively with outwardly diverging and outwardly converging radially inner and outer surfaces.
It has been found that, in addition to the improvement in the strength and quality of the seal afforded by the preferred embodiment of the invention, the further advantage arises relative to the Allsop invention that the flange can be formed `cold` after the body itself has been moulded and trimmed to its final specification. Moreover, relative to some of the embodiments of the Allsop invention, the block according to this invention is simpler by virtue of being a one-piece member not requiring assembly with a separately moulded end cap.
It has been mentioned that the forming tool 50 may, if desired, be rotated. Alternatively, of course, the mould case 44 could be rotated while the forming tool engages with the block. Such rotation of the tool and/or the mould case could be useful when forming the blocks from relatively hard adhesive. The rotation causes additional friction the resulting heat from which aids the forming.
It is further envisaged within the scope of this invention to form a plurality of concentric seals, or to form a single seal intermediate the ends of the block, or to form seals additional to the rear seal. In other words, there may be a sole seal-forming flange not at or adjacent to the rear of the block, but somewhere intermediate the ends. When using more than one such block placed end-to-end in the gun, the rearmost block will receive compressed air and push the front block or block part forwardly, whether or not the seal of the front block has been consumed by the application of heat. The gun will then need reloading when the seal of the rear block has been consumed.
In FIG. 11, a variant of the block is shown. Here the block is designated 110, and has plain front and rear ends 111, 112, respectively. The body 110 is provided with a plurality of similarly sized flanges 113. As shown, the flanges 113 are parallel and equispaced, but this is merely optional, rather than essential. Also, all the flanges 113 are shown as flaring outwardly and rearwardly. However, if desired, some of the flanges may flare outwardly and forwardly, in which case the block 110 becomes usable in either longitudinal orientation, thus reducing or eliminating the need for unskilled personnel to take care when loading.
Each flange 113 is thus shaped and dimensioned resiliently, yieldingly and sealingly to engage the bore or internal feed passage of a dispenser gun.
The flanges 113 are preferably formed by a process analogous to turning and spinning on a lathe.
In FIG. 12, the block 110 has a plurality of contiguous closed annular ridges or rings 113 constituting the sealing flanges. The rings 113 are concentric, equispaced and parallel, although these are merely preferred features. The rings 113 are preferably formed by a cold-rolling process, although a pressure-forming process may also be used. The profile of the threads may be varied as desired.
It will be noted in connection with FIGS. 11 and 12 that the rearmost flange 113 need not be closely adjacent the rear end 112 of the block 110.
In the various manufacturing processes mentioned above, to which moulding should be added, problems arise from the need to balance the thermal, mechanical and adhesive properties of the material used. Clearly the seal(s) formed must be rigid enough to be efficient, yet they must be yielding to allow the block to be advanced by compressed air. On the other hand, if the process imparts too much heat to the material, it will melt and stick. This means that there must be careful choice of mould release agents and coolants, closely to localise the transfer of heat. Yet again, most suitable materials have considerable inherent resilience which means that any cuts made into a body of the material must be "oversize" to allow for the tendency of the material to spring back into its former shape.
It is known to apply adhesive to a workpiece by means of a dispensing device which has a feed passage charged with an elongated mass of adhesive which at room temperature is non-liquid, substantially non-tacky, and substantially shape-retaining; the device includes means for melting a part of the adhesive block, a dispensing outlet for dispensing adhesive in substantially liquid form, and means for supplying pressurised fluid for advancing the adhesive block along the feed passage towards the dispensing outlet. Such a dispensing device will hereinafter be referred to as "an adhesive dispenser of the type defined".
The Allsop invention sought to simplify the design of the adhesive mass, enabling in turn the mechanical construction of the dispenser to be simplified by obviating the need for a piston which was employed in prior art dispensers to propel the adhesive block. Accordingly, the Allsop invention disclosed and claimed a solid adhesive member made of hot-melting material for use in an adhesive dispenser which dispenser includes a feed passage, means for melting a part of the adhesive member, a dispensing outlet for dispensing adhesive in substantially liquid form, and means for supplying pressurised fluid for advancing the adhesive member along the feed passage towards the dispensing outlet, wherein the adhesive member is formed at or adjacent the rear end thereof, (relative to the direction of its advance in use) with a flange shaped and dimensioned so as to be capable of being advanced along the feed passage in substantially fluid-tight sealing engagement therewith, said rear end, including the flange, serving in use as a piston face for the direct application of pressurised fluid thereto.
In a preferred embodiment of the Allsop invention, the rear end of the adhesive block is concave or includes a recess, cavity or other opening. This has the advantage that application of fluid pressure to the rear end will cause pressure to be exerted not only in the axial, i.e. advancing direction, but also peripherally against the flange, whereby to help maintain the latter in satisfactory sealing relationship with the internal bore of the feeding passage.
While this invention has the same broad aims as the Allsop invention, viz. the simplification of the design of the dispensing device by obviating the need for a piston, this invention has the additional aims of providing varying configurations of the block and flange or flanges; improving the quality of the seal between the adhesive block and the feed passage; and improving the resilience of the seal-forming flange or flanges formed on the adhesive block. Further aims of the invention include the provision of a plurality of processes for manufacturing the adhesive block. In one preferred process, the flange(s) may be formed after the block has been moulded and trimmed to size, and wherein the configuration of the seal-forming rear end may be varied.
According therefore to one exemplary aspect of this invention, there is provided a solid adhesive block made of hot-melting melting material for use in an adhesive dispenser of the type defined, wherein the end of the adhesive block which, relative to the direction of its advance in use, is the rear end, is provided with a peripheral flange shaped and dimensioned so as to constitute a resilient, rearwardly and outwardly projecting sealing portion, the latter being separated from the central portion by a recess, whereby in use the direct application of pressurised fluid to said rear end will cause the block to be advanced along the feed passage with the flange in resilient yet fluid-tight sealing engagement therewith.
A portable adhesive dispensing device in the form of a trigger-actuated gun is known wherein the gun has a barrel portion containing said feed passage of a length sufficient to accommodate at least one adhesive block and the remainder of another previously already used block placed end-to-end. Actuation of the trigger causes compressed air to be applied to the rearmost block by way of a piston.
It is also often found that on loading the barrel an air lock may form between the front end of the rear adhesive block and the rear end of the front adhesive block or block part. Such an air lock is obviously undesirable from the viewpoint of continuous and uniform dispensing of adhesive. Moreover, when the uncovered end of a block is place adjacent the piston, some undesired adhesion between the block and the piston may occur.
Bearing in mind that such guns are frequently operated by relatively unskilled personnel, certain preferred embodiments of this invention seek to eliminate the above-mentioned disadvantages by virtue of the fact that the different shapes of the front and rear ends of the adhesive block will enable an operator to distinguish between said ends and to load the gun correctly, and by obviating the need for a piston.
Preferably, the adhesive block is a one-piece cylindrical member with a substantially planar front end and a substantially planar rear end or central portion, said flange being annular.
Advantageously, said recess may be a groove of substantially V-shaped cross-section.
In one optional embodiment, the radially inner and radially outer surface of the annular flange are forwardly or rearwardly convergant. Preferably, the flange and the central portion of the rear end terminate in the same transverse plane.
According to another exemplary aspect of the invention, there is provided a process for making a solid adhesive block as set forth above, the process comprising providing a mould having a bevelled wall portion, disposing an adhesive block in the mould so that one end of the block is located adjacent the said bevelled wall portion, deforming the periphery of said one end of the block against the said bevelled wall portion and cutting a recess in said end so as to form an outwardly extending peripheral flange separated by a recess from the central portion of said one end.
Preferably the deforming and cutting steps are carried out by a bevelled forming tool.
The angel of bevelling of the forming tool may be the same as, or may be smaller than, that of the bevelled mould wall portion; in the latter case, the flange produced thereby will have a feathered edge.
According to yet another aspect of the invention, there is provided a solid adhesive block made of hot-melting material for use in an adhesive dispenser of the type defined, wherein the block is provided with a plurality of spaced apart flanges along its length, each flange being capable of forming a resiliently yielding seal with the internal bore of the dispenser. The flanges may be substantially ring-shaped and formed by a process akin to cold-rolling or pressure-forming. Alternatively, they may project rearwardly with feathered edges, produces by turning involving a plough-shaped cutting tool. The presence of a plurality of seals obviously improves the overall quality of the seal between the block and the bore in the dispenser.
Alternative preferred embodiments of the invention seek to provide adhesive blocks which are capable of being inserted into a dispensing gun in either longitudinal orientation, the blocks having a plurality of featherededge seals, with some feathered edges "pointing" forwardly (in relation to the direction of advance of the block in use) and others pointing rearwardly.
The invention also includes in its scope apparatus for carrying out the processes set forth above, and also products made by said processes and by said apparatus.
The hot-melt adhesive is well-known as such and may, for example, be made of a polyamide resin or a polyester resin or an ethyl-vinyl-acetate (EVA) resin, or of any suitable mixture of these. The adhesive may incorporate wax(es), filler(s), or extender(s) and additives to influence the viscosity, melting point or other physical property of the adhesive block.
The invention is illustrated, by way of example only, with reference to the accompanying purely schematic drawings, wherein
FIGS. 1 to 3 are respective sectional views of successive stages of a pressure-forming process for making an adhesive block, according to the present invention,
FIGS. 4 and 5 show an adhesive block, respectively in elevation and in section, before the process is carried out, i.e. before the block is placed in the mould case shown in FIG. 1,
FIGS. 5 to 8 illustrate, respectively in elevation and in two mutually normal cross-sections an adhesive block according to the invention and made by the process shown in FIGS. 1 to 3, FIG. 8 being a section along line A--A in FIG. 7,
FIGS. 9 and 10 respectively illustrate a variant of the forming tool shown in FIGS. 1 to 3, whereby adhesive blocks according to the invention may be fabricated with a sealing portion having a feathered edge, and
FIGS. 11 and 12 respectively illustrate variants of the adhesive block, FIG. 11 showing a variant formed by a turning process e.g. on a lathe, while FIG. 12 shows a variant formed by cold-rolling.
Referring first to FIGS. 1 to 3, a pressure-forming process for making a hot-melt adhesive block according to the invention is illustrated. From the resin material an elongated, substantially cylindrical body 40 is made by a previous moulding process. The ends 41 and 42 of the body are planar and transverse to the central longitudinal axis 43 of the body 40. The body 40 is then placed (FIG. 1) in an annular mould case 44 which may or may not be the same as was used to mould the body 40.
The mould case 44 has a cylindrical outer surface. One end of the inner surface 45 is, however, chamfered or bevelled as shown at 46. The angle of bevelling is predetermined.
The mould case 44 is arranged to cooperate with a forming fool 50 which is displaceable, by any suitable means not shown, along the axis 43 towards and away from the mould case 44. The tool 50 may, if desired, be additionally rotatable about that axis. It has a frusto-conical end 51, the cone angle of which is substantially identical with the angle of bevelling of the part 46 of the inner surface 45 of the mould case 44. As shown by chain lines, the forming tool 50 has a cylindrical recess 52 extending from the bottom of the frusto-conical end 51. The cylindrical external surface 53 of the forming tool has a diameter which is equal to or greater than the diameter of the inner surface 45 of the moulding case 44, but is smaller than the maximum diameter of the bevelled part 46.
As shown by the sequence in FIGS. 1 to 3, when the forming tool 50 is pressed into the body 40 along the arrow 55, and then withdrawn, the end 42 of the body 40 will be cut and deformed into the configuration best appreciated from FIG. 8. In other words, an annular recess or groove 56 of V-shaped cross-section is cut in the end 42 which groove separates an unaltered central portion 57 from a peripheral portion or flange 58. The flange 58 is shaped by deformation between the part 46 and the frusto-conical end 51 and can be seen to be an outwardly and upwardly flaring annular flange with substantially parallel radially inner and outer surfaces.
FIGS. 4 and 5 on the one hand, and FIGS. 6 to 8 on the other hand, respectively illustrate the body 40 before and after the process shown in FIGS. 1 to 3 has been carried out.
In use, the flanged body 40 may be fed into a piston-less fluid pressure operated portable adhesive dispenser. The body 40 is loaded with the plain end 11 as the front end, while the end 42 with the flange 58 will be the rear end, the flange and the central portion 57 together constituting a piston face for the direct application of fluid pressure thereto. The dimensions of the mould case and of the forming tool are so chosen that the maximum outer diameter of the flange 58 is somewhat greater than the diameter of the feed passage in the dispenser. By virtue of the resilience and shape of the flange 58, it will in use be in fluid-tight, sealing yet yielding engagement with the wall of the feed passage so that the body or block may advance therealong under the action of the applied fluid pressure.
The presence of the groove 56 of V-shaped cross-section has two important functions. Firstly, it assists in imparting resilience to the flange 58. Secondly, in use, the application of fluid pressure to the rear end 42 will cause pressure to be exerted within the groove 56 with a radially outward component which helps to maintain the flange in sealing engagement with the feed passage.
It will be appreciated that by varying the cone angle of the forming tool and the cooperating angle of bevelling in the mould case, the shape of the flange 58 may be varied.
FIGS. 9 and 10 illustrate variants of the forming tool 50, the differences being in the respective cone angles of the respective frusto-conical ends 51a and 51b. By varying the cone angle in this way, but maintaining the angle of bevelling of the part 46 of the mould case 44, the resulting flange 58 will have a feathered edge, respectively with outwardly diverging and outwardly converging radially inner and outer surfaces.
It has been found that, in addition to the improvement in the strength and quality of the seal afforded by the preferred embodiment of the invention, the further advantage arises relative to the Allsop invention that the flange can be formed `cold` after the body itself has been moulded and trimmed to its final specification. Moreover, relative to some of the embodiments of the Allsop invention, the block according to this invention is simpler by virtue of being a one-piece member not requiring assembly with a separately moulded end cap.
It has been mentioned that the forming tool 50 may, if desired, be rotated. Alternatively, of course, the mould case 44 could be rotated while the forming tool engages with the block. Such rotation of the tool and/or the mould case could be useful when forming the blocks from relatively hard adhesive. The rotation causes additional friction the resulting heat from which aids the forming.
It is further envisaged within the scope of this invention to form a plurality of concentric seals, or to form a single seal intermediate the ends of the block, or to form seals additional to the rear seal. In other words, there may be a sole seal-forming flange not at or adjacent to the rear of the block, but somewhere intermediate the ends. When using more than one such block placed end-to-end in the gun, the rearmost block will receive compressed air and push the front block or block part forwardly, whether or not the seal of the front block has been consumed by the application of heat. The gun will then need reloading when the seal of the rear block has been consumed.
In FIG. 11, a variant of the block is shown. Here the block is designated 110, and has plain front and rear ends 111, 112, respectively. The body 110 is provided with a plurality of similarly sized flanges 113. As shown, the flanges 113 are parallel and equispaced, but this is merely optional, rather than essential. Also, all the flanges 113 are shown as flaring outwardly and rearwardly. However, if desired, some of the flanges may flare outwardly and forwardly, in which case the block 110 becomes usable in either longitudinal orientation, thus reducing or eliminating the need for unskilled personnel to take care when loading.
Each flange 113 is thus shaped and dimensioned resiliently, yieldingly and sealingly to engage the bore or internal feed passage of a dispenser gun.
The flanges 113 are preferably formed by a process analogous to turning and spinning on a lathe.
In FIG. 12, the block 110 has a plurality of contiguous closed annular ridges or rings 113 constituting the sealing flanges. The rings 113 are concentric, equispaced and parallel, although these are merely preferred features. The rings 113 are preferably formed by a cold-rolling process, although a pressure-forming process may also be used. The profile of the threads may be varied as desired.
It will be noted in connection with FIGS. 11 and 12 that the rearmost flange 113 need not be closely adjacent the rear end 112 of the block 110.
In the various manufacturing processes mentioned above, to which moulding should be added, problems arise from the need to balance the thermal, mechanical and adhesive properties of the material used. Clearly the seal(s) formed must be rigid enough to be efficient, yet they must be yielding to allow the block to be advanced by compressed air. On the other hand, if the process imparts too much heat to the material, it will melt and stick. This means that there must be careful choice of mould release agents and coolants, closely to localise the transfer of heat. Yet again, most suitable materials have considerable inherent resilience which means that any cuts made into a body of the material must be "oversize" to allow for the tendency of the material to spring back into its former shape.