Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C53/00—Shaping by bending, folding, twisting, straightening or flattening; Apparatus therefor
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
  • F16F1/00—Springs
  • F16F1/36—Springs made of rubber or other material having high internal friction, e.g. thermoplastic elastomers
  • F16F1/366—Springs made of rubber or other material having high internal friction, e.g. thermoplastic elastomers made of fibre-reinforced plastics, i.e. characterised by their special construction from such materials
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C53/00—Shaping by bending, folding, twisting, straightening or flattening; Apparatus therefor
  • B29C53/02—Bending or folding
  • B29C53/12—Bending or folding helically, e.g. for making springs
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C53/00—Shaping by bending, folding, twisting, straightening or flattening; Apparatus therefor
  • B29C53/56—Winding and joining, e.g. winding spirally
  • B29C53/58—Winding and joining, e.g. winding spirally helically
  • B29C53/581—Winding and joining, e.g. winding spirally helically using sheets or strips consisting principally of plastics material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C53/00—Shaping by bending, folding, twisting, straightening or flattening; Apparatus therefor
  • B29C53/80—Component parts, details or accessories; Auxiliary operations
  • B29C53/82—Cores or mandrels
  • B29C53/821—Mandrels especially adapted for winding and joining
  • B29C53/824—Mandrels especially adapted for winding and joining collapsible, e.g. elastic or inflatable; with removable parts, e.g. for regular shaped, straight tubular articles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
  • B29K2105/06—Condition, form or state of moulded material or of the material to be shaped containing reinforcements, fillers or inserts
  • B29K2105/08—Condition, form or state of moulded material or of the material to be shaped containing reinforcements, fillers or inserts of continuous length, e.g. cords, rovings, mats, fabrics, strands or yarns
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
  • B29L2031/00—Other particular articles
  • B29L2031/774—Springs
  • B29L2031/7742—Springs helical springs

Definitions

• the present invention relates to a fiber reinforced plastic spring and a method of manufacturing the same.
• a metal spring may be destructed in a corrosive environment and, accord ⁇ ingly, a steel spring applied in a saline environment like e.g. seawa- ter, is thus exposed to an accelerating corrosion with an ensuring deterioration of the spring properties.
• springs applied in an environment with temperatures below freezing point brittleness phenomena may occur, and consequently there is a risk of the spring going to pieces when exposed to load.
• Another drawback of metal springs is the occurence of fatigue fractures, which come about after the spring has been exposed to a certain number of stresses, even though each stress is below the tensile strength capacity of the mate ⁇ rial .
• the uncured fiber reinforced plastic is placed in the manufacturing tool, and the spring is subse ⁇ quently cured. After the curing of the spring it is separated from the manufacturing tool.
• the strength obtained is not as high as in comparably sized steel springs, and the manufacture is time and labour consuming.
• this object is achieved with a me ⁇ thod, which is characterized in that the fiber reinforced plastic ma ⁇ terial is provided in the form of tapes cured under tension with the fiber material arranged in the longitudinal direction, that at least one tape is placed on a mandrel having a configuration depending on the configuration of the spring to be manufactured, which tape is placed with its longitudinal direction orientated substantially along the intended final configuration of the spring, that the tape is se ⁇ cured to the mandrel since the ends thereof are placed in gripping means, that the tape is provided with a glue material permitting it to be glued together with one or more substantially corresponding tapes, which are secured in the gripping means, too, that a number of tapes are used in order to provide a laminate with the number of layers and the dimensions desired, that the laminate having substantially the desired final configuration of the spring is glued together on the mandrel as the glue material undergoes a chemical process during which gluing occurs and that the glued form stable spring is removed from the mandrel and the chemical
• Tape as defined in the present specification and claims means an elon ⁇ gated element, the cross section of which has a width to height ratio within the range of 5 to 100 or even higher and which has a substan ⁇ tially infinite longitudinal extension compared to the width of the element.
• the tapes to be used are precured under tension a material is obtained having properties that are comparable with the properties obtained in prestressed concrete and laminated wood. Accordingly, a starting material of very high strength is obtained.
• This starting material consisting of cured tapes is used for the manufacture of the laminate.
• glue material allows a small mutual displacement of the individual layers in case several tapes- are simultaneuosly wound around a mandrel.
• the tapes are bound together as the glue material undergoes a chemical process. In this way a laminate is made, the inner dimension and form of which is determined by the mandrel.
• the gripping means need only prevent the tape(s) from "swishing" away from the mandrel.
• the inner dimension of the spring is determined by the outer form of the mandrel .
• the mandrel may be produced with any desired configuration for the manufacture of coil springs, spiral springs, volute springs etc. Ac ⁇ cordingly, for the manufacture of a coil spring solely a cylinder with a smooth surface is required and a smooth cone formed mandrel may be used for manufacturing a spatial spiral spring.
• the constant pitch may be ensured by positioning guide pins in the mandrel or by using a spindle governed displacing of the mandrel when laying up the tapes.
• a spind ⁇ le governed pitch makes it possible, with one mandrel, to manufacture a large number of springs having different pitches, in that the pitch of the individual spring is defined by a simple regulation following the same principle as the one used with a lathe.
• the method is characterized in that a number of tapes necessary for the required spring dimensions, and which are cured under tension, are provided with a specific glue material and are put together to produce the laminate, that said la ⁇ minate in assembled state is placed on the mandrel, whereafter said gluing together is provided as the glue material undergoes a chemical process whereby the gluing together occurs and that the glued together spring is removed from the mandrel.
• This embodiment is particularly suitable when a spring is to be manu ⁇ factured under conditions not allowing for the individual winding up of the tape, e.g. due to the configuration of the mandrel, or when it is desirable to lay up a laminate comprising all tapes at a time to obtain advantages of production, e.g. in the form of a quicker laying up.
• this method is especially advantageous when a spiral spring is to be manufactured, in the case of a flat spiral spring as well as in the case of a spatial or conical spiral spring.
• a mandrel or a mould is used filling up the space between the coils of the spiral spring, preferably provided in the form of an insertion, which is wound together with the laminate having tapes between which the glue material is provided, said glue material not having undergone a chemical process at the time of the winding.
• the individual tapes will be able to conduct a mutual displacement during the winding, and the forces required for the wind ⁇ ing will not be inconveniently great.
• a mandrel or a mould is used, which, too, fills up the space between successive coils.
• the laminate is wound on a mandrel in order to obtain the inner diameter and subsequently the laminate is wound together with an insertion placed between successive ⁇ sive coils, during which winding an axial displacement of the mandrel, on which the first coil has been laid, is effected.
• This axial dis ⁇ placement is adapted to the winding speed, so as to provide a spring with the desired pitch.
• the mandrel and/or the insertion placed between the coils of the spring may be removed when the chemical process has progressed suffi ⁇ ciently for the spring to be form stable. Thereafter the chemical pro ⁇ cess may continue, and simultaneously the mandrel and the insertion may be used for the manufacture of a new spring.
• a number of mandrels may advan ⁇ tageously be placed in a production unit, e.g. on a round table, the cycle time of which corresponds to the time required for the laying up of a spring plus the mould time of the spring on the mandrel plus the time required for removing the spring. Accordingly, it is possible to perform the method continously in successive stations and, thus, to obtain an optimum utilization of the mandrels.
• the chemical process is a curing process and the glue material undergoes a heat curing while placed on the mandrel thus allowing for a substantial reduction of the mould time of the spring on the mandrel. After heat curing on the mandrel the spring is removed and aftercured at room temperature.
• the fiber reinforced plastic materi ⁇ al comprises an epoxy resin
• the glue material used is based on an epoxy resin, too.
• Tests with epoxy resins have proved it possible to obtain satisfactory results with a fiber content as high as 80%. How ⁇ ever, it is also possible to use polycarbonates for the fiber rein ⁇ forced plastic material as well as for the glue material.
• springs have been made of tapes each having a width of 20 mm and a thickness of mm, and which are provided in a number of 40 to obtain a substantially square section of 20x20 mm and coil springs were wound with an inner diameter of approximately 100 mm.
• the assembly was heated to a temperature of about 140°C, and after about 3% minutes it was pos- sible to separate the spring from the mandrel as the spring was now form stable. Then the spring aftercured for 48 hours at room tempera ⁇ ture to obtain maximum strength.
• epoxy resin a fiber con ⁇ tent of 80% was used and the glue material used was based on the same epoxy resin.
• the spring may be manufactured by means of a mandrel without any grooves or tracks it is possible to provide manu ⁇ facturing tools at very low costs.
• a tool in the form of a round steel bar hav ⁇ ing an outer diameter corresponding to the inner diameter of the spring plus the tapes and glue material required.
• This single tool permits the manufacture of a large number of coil springs having dif ⁇ ferent pitches and having varying spring characteristics since the laminate may be provided with larger or smaller number of tapes, ac ⁇ cordingl tape ' s of different sizes may be used, too.
• a spring for most of the intended fields of the application may be manufactured with sufficient accuracy on a mandrel provided with guides or spacers at spaced apart positions on the mandrel.
• a test made with a coil spring manufactured with an inner diameter of 100 mm has shown that said inner diameter after removal was increased by a magnitude of a few hundredth of a millimeter only.
• the following ratios between the different dimensions may be used cross section of spring: 40x40 mm, inner diameter of spring: 300 mm, to this spring tapes each having a width of 40 mm and having a thick ⁇ ness of between about ⁇ mm to 2 mm may be used.
• the greater the inner diameter of the spring the greater the thicknesses of the individual tapes.
• a lower limit for the thickness of the tapes exists, being at about 0.2 mm. A thickness below this limit will cause productional difficulties which substantially obstruct the use of a smaller thickness.
• Ffg. 1 is a diagrammatic side view of a tool for use in the 0: manufacturing of a coil spring and
• Ffg. 2 an end view of the tool shown in Fig. 1.
• Ffg. 1 illustrates diagrammatically a tool for use in the manufactur ⁇ ing of a coil spring 1 according to the present invention.
• the coil spring 1 is manufactured of a number of elongated tapes 2, precured while under tension and having the fiber material arranged in the longitudinal direction of the tapes.
• the elongated tapes 2 are wound simultaneously around a cylindrical mandrel 3, which 0 may optionally be hollow or solid.
• the exemplary mandrel is provided with gripping means 4 consisting of a plate 5, two thread bars 6, two nuts 7 and two guides 8, mounted on the mandrel 3 either by welding or by other suitable securing means.
• the nuts 7 are provided in the form of w ⁇ ng nuts, as they may hereby be tightened by hand.
• the wing nuts are secured to the thread bars 6.
• the guides 8 are at their end parts re ⁇ mote from the mandrel 3 bent down, and threaded holes are provided in the bended parts 8', which holes are intended for engagement with the D " thread of the thread bars 6 to press the tapes 2 positioned below the plate into contact with the mandrel 3 when the thread bars are screwed against the plate 5.
• the thread bars 6 are shown as substantially screwed home. 5
• the gripping device 4 is only intended to hold the tapes in order for them not to "swish" away from the mandrel, thus said gripping device does not need to exercise great squeezing force, the tension occuring in the longitudinal direction of the tapes being rather small.
• the mandrel 3 is provided with spacers 9 placed diametrically opposed on the mandrel 3.
• the spacers 9 are mounted on the outer surface of the mandrel.
• spacers which may be retracted into a hollow or partly hollow mandrel 3, which facilitates the removel of the form stable spring 1 from the mandrel.
• the spacers 9 may be replaced by detachable spacer blocks or optionally pins for guiding the pitch of the spring 1 on the mandrel 3.
• the mandrel is rotatable in a support 11, which support may be provided with drive means (not shown) enabling rotation of the mandrel when laying the tapes 2.
• the mandrel 3 is also supported so as to permit rotation.
• the mandrel 3 may, as known, be dismantled from the supports 11 when the spring 1 is to be removed.
• the illustrated coil, spring 1 is manufactured by the tapes 2, precured under tension with the fiber material arranged in the longitudina-1 direction, being placed simultaneously on the mandrel 3, said tapes being previously provided with a heat curable glue material.
• One end of the surmounted tapes 2 is placed in the gripping device 4 and is secured between the surface of the mandrel and the plate 5, which is screwed against the mandrel.
• the glue provided tapes are wound around the mandrel, which is simultaneously rotated slowly by the drive means, not shown, during this rotation it is solely neces ⁇ sary to exert a slight traction in the direction of the arrow 12, and during this laying the tapes may perform a mutual displacement in or ⁇ der to adapt itself to the different winding diameters.
• tapes 2 having equal lengths are used in the manufacturing of the coil spring 1 these tapes will produce different extensions at the end of the coil spring as illustrated in Fig. 2.
• tapes 2 of different lengths may be used to ensure that the tapes have sub- stantially the same extension at the opposite end of the coil spring, however, this does not cause any technical problems.
• the ends of the spring may be cut according the intended application.
• the spring 1 is heated by heating means (not shown) for a period permit- ting at least a partial heat curing of the glue material, and subse ⁇ quently the spring may be removed from the mandrel 3 and aftercured at room temperature.
• the heating means used may be provided in the form of heating means positioned either inside or outside the mandrel, e.g. in the form of an outer heating tunnel which, following the positioning of the spring on the mandrel, is moved over the mandrel and over the spring placed thereon and is held in this position for the period wherein the heat curing of the glue material is desired.
• the fiber reinforced coil spring 1 it is possible to use a very simple manufacturing tool and, as illustrated- in the drawing, it is possible in principle to use only one smooth cylinder for the manufacturing of coil springs with diffe- rent characteristics.
• said smooth cylinder determines the inner diameter of the coil spring it is possible to vary the widths of the tapes, the thicknesses of the tapes, the number of tapes, and the pitch may thus be determined by detachable spacer blocks placed be ⁇ tween the coils of the coil spring.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Moulding By Coating Moulds (AREA)
• Springs (AREA)
• Laminated Bodies (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

Family

ID=8109434

Family Applications (1)

Country Status (4)

Cited By (2)

Families Citing this family (1)

Citations (5)

• 1987
  • 1987-04-15 DK DK200987A patent/DK200987A/da not_active Application Discontinuation
• 1988
  • 1988-04-15 AU AU16890/88A patent/AU1689088A/en not_active Abandoned
  • 1988-04-15 KR KR1019880701658A patent/KR890700461A/ko not_active Application Discontinuation
  • 1988-04-15 WO PCT/DK1988/000069 patent/WO1988007927A1/en unknown

Patent Citations (5)

Non-Patent Citations (1)

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