Patent ID: 12252356

Further advantages and aspects of our systems and methods are derived from the description of examples explained hereunder by the figures.

DETAILED DESCRIPTION

The schematic general illustration inFIG.1shows an example of a manufacturing system100of producing coil springs from wire. The coil springs are also referred to as “springs,” and the manufacturing system is referred to as “system.”FIG.2shows details of the spring coiling machine of the system, having components of a camera-based measuring system, and of the pneumatic conveyor system.

An automatic spring manufacturing machine in the form of a CNC spring coiling machine200is part of the system. The CNC spring coiling machine200has an infeed installation210equipped with infeed rollers and feeds successive portions of a wire D by way of a numerically controlled advancing speed profile in the horizontal direction into the region of a forming installation220. To this end, the wire, coming from a wire reserve (coil)110kept ready on a reel, is drawn and guided through a straightening unit (not shown). The wire D, with the aid of numerically controlled tools of the forming installation220, in a spring coiling operation is formed to a coil spring F. The forming tools include two numerically controlled winding pins222,224, which are disposed to be offset at an angle of 90° and are aligned to be radial to the desired spring axis, and at least one pitch tool226to at any time predefine the local pitch of the developing spring in a numerically controlled manner (seeFIG.2). Furthermore provided is a cutting installation which after the completion of a forming operation severs a finished coil spring F from the supplied wire by way of a linear operating movement. The machine axes of the CNC machine associated with the movable components are controlled by a computer-numerical control installation230.

The spring coiling machine200is equipped with a camera-based optical measuring system for the real-time, contactless detection of data pertaining to the geometry of a currently produced spring. Part of the measuring system is a CCD video camera250which is installed such that the field of vision thereof can detect a portion of the developing spring close to the tools of the forming installation, as well as a further video camera260by way of which the spring length can be determined. Data pertaining to the spring geometry of the produced spring can be determined from the camera images by image detection, the data in a computer of the control installation230being compared with corresponding data pertaining to a desired target geometry. As a result, it is possible for the spring coiling process to be monitored while a spring is being created, and optionally by way of feedback of measured values to feedback-control the spring coiling process by changing the actuated values of tools (in-process feedback-control). Moreover, it is possible to identify almost simultaneously with the production of the spring whether the produced spring is a good part (spring geometry in the tolerance range) or a bad part (spring geometry outside the tolerance range) which is to be removed. The optical measuring system functions as a component part of a quality detection system.

The coil spring F can be a coil compression spring or a coil tension spring, each having a cylindrical design or a design deviating from the cylindrical. In cylindrical coil springs, the spring diameter is constant across the length of the springs but can however also vary across the length such as in conical or barrel-shaped coil springs, for example. The overall length of the (unstressed) spring can also vary greatly for different applications.

The spring coiling machine can be constructed and operate as described in DE 10 2010 014 385 B4. Other design examples are also possible.

After being severed from the wire, the severed coil springs F with the aid of a pneumatic conveyor system300are successively conveyed automatically, in the cycle of the spring coiling machine by a compressed air flow, to a downstream machine400which is or can be at a distance of several meters from the spring coiling machine.

FIG.2shows the entry end of the conveyor system that faces the spring coiling machine, having a spring suction installation320connected to a compressed air source322and in the cycle of the machine suctions the completed coil springs into the pipeline310of the conveyor system300. The machine-distal measuring camera260can detect the front end of the coil spring through a window312in the wall of the spring suction installation320(cf.FIG.2) without interference.

The downstream machine400(exactly like the conveyor system300) is a component part of the complete system100and is configured for carrying out downstream operations on the supplied coil springs. The downstream machine comprises a heat treatment unit for a controlled heat treatment of the freshly wound springs. Installations for quality control of the heat-treated springs and for sorting and relaying the latter to at least one downstream plant500are integrated.

The downstream machine400comprises an internal transport unit410which by a rotary drive is rotatable about a vertical rotation axis412. The transport unit410has a multiplicity of vertically aligned spring receptacles420which are disposed to be outside the axis of the rotation axis of the transport unit410and are intended to in each configuration receive a single coil spring F for machining. The spring receptacles are disposed in the form of a ring about the rotation axis412.

The spring receptacles420are formed substantially by cylindrical sleeves from an electrically non-conducting, torsion-resistant and temperature-resistant material. The upper and the lower ends of the vertically aligned spring receptacles are fastened in an upper ring422and a lower ring424, respectively, the rings422,424being connected to one another in a rotationally fixed manner and supporting the spring receptacles (cf.FIG.5). The overall construction of the rotatable components here is also referred to as the loading plate410. A support ring426which does not rotate and is made from a wear-resistant material is assembled below the loading plate, the wear-resistant flat horizontal upper side428of support ring426being disposed at a minor spacing below the spring receptacles. The received springs are supported on this upper side.

A plurality of workstations of the downstream machine400are disposed about the external circumference of the transport unit410, the plurality of workstations during the operation of the downstream machine being successively approached by a coil spring disposed in a spring receptacle430in that the transport unit is rotated. The plan view from above inFIG.3shows a preferred configuration. A spring receptacle is loaded with a single coil spring from vertically above at a loading station430. The installations of the pneumatic conveyor system300provided to this end will yet be explained in more detail at a later stage (cf.FIG.5, for example).

A heating station440in which the heating of the coil spring is carried out by induction, for example, or by conduction of a heating current, is situated to be disposed downstream of the transport unit in the transport direction TR. Following thereafter are, for example, four cooling units450-1,450-2,450-23,450-4of a multi-stage cooling station450, which are connected to a cold air blower and with the aid of cooled air cool the coil springs, which initially are still heated to several 100° C., in steps to at least a lukewarm temperature (40° C. or less). Internal stress in the spring wire, resulting from the forming operation, for example, is dissipated by the heat treatment, and any potentially generated magnetization is removed.

Following therefrom in the transport direction is a setting station455in which a setting operation can be carried out. The latter is typically used in the manufacture of coil compression springs for the following reason. Should the shear stress exceed the permissible value when the spring is loaded, a lasting deformation arises which manifests itself in the reduction of the unstressed length. In the field of spring technology, this procedure is referred to as “setting,” this being associated with the characteristics of “creeping” and “relaxation” known from field of materials engineering. To counteract this setting procedure, the compression springs are wound to be longer by the expected setting value and subsequently compressed to the block length in a setting operation. This pre-setting enables a better material capacity and a higher load.

Following therefrom in the transport direction is a measuring station460which in the exemplary configuration is conceived as a length measuring station to measure the spring length present between the axial ends of the coil spring after the completion of the heat treatment and optionally of the setting operation. Alternatively or additionally, diameter values can also be measured, for example. The measured values are compared with corresponding target values to establish whether the spring is a good part (IO, in order), which is within the production tolerances, or a bad part (NIO, not in order), the characteristics of the latter not corresponding to the specification.

Following in the circumferential direction are a plurality of ejection stations at which a spring is ejected from the downstream machine as a function of the characteristics established on the spring. The bad parts (NIO) are removed from the spring receptacle at the ejection station470-1and ejected into a collection container NIO. In this way, only good parts make their way to the following ejection stations. The directly following ejection station470-2serves for a sporadic, more exact quality control procedure (Q, quality control). Coil springs are ejected at comparatively small or large intervals, according to a predefined checking profile, for a more exact quality control procedure. The coil springs then land in the collection container Q. The following ejection station470-3serves for ejecting those coil springs (good parts, IO) which are provided for further machining or further processing, thus for the further production process. The springs make their way to the downstream plant500. Finally, there is also an empty checking station480where it is checked whether the spring receptacle which as the next is cycled onwards again to the loading station430is empty as expected, or by virtue of a malfunction still contains a coil spring (or other material) which would interfere with any loading in the downstream loading station430.

This configuration is illustrated only by way of example. More or fewer than four cooling units can also be present in the cooling station. Optical measuring of the length instead of a tactile length measurement can also be provided at the measuring station. Alternatively or additionally, other geometric parameters of a spring, for example, the diameter thereof, or the diameter profile or the like, can also be detected in a measuring station. A measuring station for measuring the spring force can also be provided.

In the system100, pneumatic conveying of coil springs between individual machines or stations is provided. To this end, the pneumatic conveyor system300has, inter alia, a pipeline310provided for transporting the coil springs F, which have been produced by the spring coiling machine200and severed from the supplied wire, successively in the cycle of the production to the loading station430of the downstream machine400. Provided to this end is, inter alia, a pipeline310having a plastic hose which is several meters in length and forms the pipeline main piece311. The transport of good parts to be further processed, from the ejection station470-3to the downstream plant500, is likewise pneumatically implemented by way of a further pipeline315. Bad parts are transported from the ejection station470-3by way of a pipeline into a collection container NIO. A further pipeline leads to the unit Q for the quality control procedures that have to be sporadically carried out. Should material still be situated in the spring receptacle at the empty station430for empty checking, this material is directed to a corresponding container L by way of a pipeline.

For the springs to be ejected at the corresponding workstation, pipelines in which each open out above the corresponding workstations by way of a downward-directed introduction opening are used. A star-shaped blower nozzle428(see detail inFIG.5), having a multiplicity of radial slots, is incorporated in the support ring or supporting ring426at each workstation so that springs of the similar diameters can be supported thereon and by a compressed air pulse emanating from below can be blown away upwards into the assigned pipeline.

Further details of the pneumatic conveyor system300will now be explained additionally byFIGS.4to7. These figures each show components of a brake installation.

Disposed on the end of the pipeline310that faces the spring coiling machine200is the spring suction installation or spring suctioning installation320which is operated with compressed air from a compressed air source322and during operation suctions the respective completed and severed spring F into the conveyor system at the entry side. The construction can be identical or similar to that of the suction installation of DE 24 17 685 A1 mentioned at the outset. The inlet opening of the spring suction installation320is simultaneously the inlet opening, or entry opening, respectively, of the pipeline310and is disposed so close to the forming tools that the front end of the developing coil spring is already situated in the suction duct of the spring suction installation before the spring is severed from the supplied wire. The severed spring is then accelerated in the transport direction of the pipeline by the compressed air flow, and in the pipeline moves in the direction of the downstream machine400. To guarantee a camera-based feedback-control of the winding process during the spring adjustment despite the suction installation, the body of the spring suction nozzle320has a window324through which the developing spring can be observed by the camera260.

The pipeline310can be several meters in length. The pipeline main piece311, which adjoins the spring suction installation320at the entry side, in the example is composed of a plastic hose from polytetrafluoroethylene (PTFE) with a very smooth internal side of the pipe, which ensures that the frictional forces between the internal wall of the pipe and the spring remain low on the vast majority of the transport path. The internal diameter of the pipeline is slightly larger than the maximum external diameter of the coil spring, wherein there is sufficient radial clearance for an ideally low-friction transport, and potential curved portions of the pipe can also be passed through without compromising the transport capability.

Components of a collision-proof spring transfer system305are disposed at the opposite end of the pipeline310, thus in the region of the loading station430, directly prior to entering the spring receptacle420. The spring transfer system305is constructed such that a continuous, or uninterrupted, respectively, transfer of coil springs from the pipeline310through an exit opening375of the pipeline into assigned spring receptacles420can take place. Additionally, the construction of the components automatically ensures that springs which have passed through the exit opening375in the direction of the spring receptacle and from the latter potentially want to rebound back into the pipeline are prevented from doing so in that the return path through the exit opening is blocked.

A part of the spring transfer system is a brake installation350disposed on the end of the pipeline and thereon defines a braking track352for decelerating the incoming coil springs so intensely that the coil springs can be moved vertically upwards at a finite but not excessive speed into the spring receptacle that is ready in the loading position (cf.FIGS.4and5). The braking track is a portion of the pipeline. The coil springs offered up by the pipeline, when entering the braking track, have an entry speed vE. The exit speed vAof the coil springs when exiting the braking track is significantly reduced in comparison to the entry speed (i.e., vA<vE). The springs are not brought to a standstill but remain in motion until “arriving” in the spring receptacle. The exit speed can be just only 5% to 50% of the entry speed, for example.

The brake installation350is arranged such that the coil springs successively delivered at a mutual spacing can be dispensed, without mutual contact, in the cycle of entry and at the exit speed, through an exit opening in the direction of the spring receptacle situated in the loading position. It can be achieved as a result that the kinetic energy of the coil springs towards the end of the deceleration phase is still sufficient to reliably exit the brake installation in the direction of the spring receptacle. On the other hand, the exit speed is however so minor that a coil compression spring that has dropped into a spring receptacle, upon impacting the surface428, does not rebound so intensely that a disruption of the loading procedure, which takes place in very rapid cycles, could arise.

Additionally provided is an automatically operating blocking installation (component with a variable-diameter exit opening375) which automatically prevents that coil springs after exiting the pipeline make their way from the outlet side back into the pipeline, for example, by virtue of rebounding from the base of the spring receptacle.

An example of the brake installation which operates in a particularly reliable manner will now be explained in more detail byFIGS.4to7. The brake installation350at the entry side has a spring guide sleeve360which on the entry side thereof has an internal diameter which corresponds approximately to the external diameter of the pipeline main piece311, and for producing an air-tight connection can thus be pushed onto the latter and fastened thereto. This widened portion is adjoined by a funnel portion362which tapers conically toward the bottom and transitions to a cylindrical guide duct365, of which the internal diameter is only a few tenths of a millimeter larger than the largest external diameter of the coil springs to be guided. The spring guide sleeve360is a replacement part which is adapted to the workpiece. The axial length of the guide duct365is multiple times larger than the internal diameter thereof such that a relatively long first braking track portion is formed in which the coil spring is pacified and by virtue of dynamic friction on the internal walls, above all of the cylindrical guide portion, is already decelerated from the entry speed to a lower speed.

Adjoining toward the bottom, thus in the direction of the spring receptacle, is an automatically closing supply nozzle370which is shown in the longitudinal section inFIGS.4and5and in an isometric view inFIG.6. The supply nozzle, which can also be referred to as an exit nozzle, is attached to the lower end of the guide sleeve and fastened thereon such that a connection which is preferably airtight in the radial direction is created. The supply nozzle370has an entry-proximal sleeve-shaped base portion371which at the lower end of the guide sleeve is fastened to the lower end of the spring guide sleeve by being plugged onto the latter. The base portion on the exit side has an annular arrangement of, for example, six elastically movable fingers372of identical design, which on the exit side of the supply nozzle conjointly enclose a substantially annular exit opening375which is simultaneously the exit opening of the pipeline310of the pneumatic conveyor system310. Cover portions374in the shape of ring segments protrude radially outward on the ends of the fingers. An exit sensor379in the form of a proximity switch, which emits a signal when a spring has passed the exit opening, can be seen directly in front of the exit opening inFIG.4. The signals can be utilized for feedback-controlling the acceleration of the spring by the optimal spring speed. When using the exit sensor379to detect a coil spring exiting the exit opening, the operating control system knows at any time when a coil spring exits the conveyor system in the direction of the spring receptacle, and how many springs exit in absolute terms and per time unit.

The exit opening375is variable in terms of the diameter. The exit opening375functions as part of the brake installation350, on the one hand, and on the other hand as a blocking installation375which protects the pipeline in relation to rebounding springs.

In the system100, the internal transport unit410of the downstream machine400is controlled in such a manner as a function of sensor signals of the exit sensor that the internal transport unit is briefly shut down when an exiting coil spring is detected. Undesirable collision situations, which could lead to the deformation of coil springs and/or to damage to the installations of the machine, can be avoided as a result.

The free end portions of the fingers372conjointly form a variable-diameter portion of the supply nozzle. In the unstressed basic state, thus when no coil spring is passing through, the internal diameter dIof the exit opening375is a few percentage points (for example, between 5% and 20%) smaller than the (maximum) external diameter of the conveyed coil springs. However, the exit opening can be elastically widened to a larger passage cross section by a coil spring passing through. The elastic resilience of the free end portions of the fingers in the radial direction in this construction is substantially achieved in that a spring-elastic integral hinge portion373is each formed between the base portion371and the relatively torsion-resistant portions of the fingers372, the integral hinge portion373making it possible that the fingers pivot outwards in the radial direction and in the absence of any load assume the inner basic position thereof.

The supply nozzle370in the example is an integral component which by 3D-printing is produced from a thermoplastic synthetic material. The production by 3D-printing permits the elastic characteristics of the fingers to be rapidly and most accurately adapted to the geometric and kinetic characteristics of the spring to be conveyed.

The passage duct that leads through the supply nozzle on the entry side has approximately the internal diameter of the cylindrical supply duct365of the upstream spring guide sleeve. The diameter thereafter decreases steadily in the direction of the exit opening375such that a spring moving in the direction of the exit opening375is faced with an increasingly higher resistance to movement, the latter resulting in that the static friction between the internal sides of the elastic fingers and the external side of the spring increases the more the spring approaches the exit opening. To guarantee a long service life of the frictionally-loaded parts of the supply nozzle despite the use of a plastics material, flat anti-wear elements376from hardened steel are each recessed in the region of the end portions of the elastic fingers372, the anti-wear elements376on the internal sides of the end portions of the fingers each forming wear-resistant guide faces377that run in the axial direction. The anti-wear elements in the inward direction protrude somewhat beyond the internal side of the finger ends such that the finger ends do not come into direct frictional contact with the coil spring.

The brake installation350is a passive functional unit, thus performs its function without dedicated drives. A deceleration of the incoming coil springs in two stages is guaranteed with the aid of the brake installation350. It is mainly a pacification that takes place in the relatively long cylindrical guide duct365of the guide sleeve, and a deceleration as a result of friction takes place only to a limited extent. The majority of the braking effect is caused by the automatically closing exit nozzle370.

Because the diameter of the exit opening375after the passage of the coil spring and after the bouncing back of the elastic fingers is smaller than the external diameter of the spring that has passed through, potential rebounding of the spring that has been permitted through back into the supply duct is simultaneously blocked by the supply nozzle370, or exit nozzle370, respectively. The exit nozzle, or the exit opening, respectively, thus functions also as a blocking installation which by purely mechanical means prevents the re-entry of the spring after the latter has exited the exit nozzle. This is a substantial contribution towards a trouble-free operation of the manufacturing system, even at high cycle rates.

Further elements which have a braking effect can be provided. The sectional illustration inFIG.5shows an example in which a magnetic brake unit380having at least one magnet382is part of the brake installation. The components of the magnetic brake unit on the downstream machine400are assembled on the loading station430of the latter such that the magnets are situated in direct proximity of the external side of the spring receptacle430when the latter is situated in the loading position. As a result, a coil spring introduced into the spring receptacle can be decelerated with the aid of magnetic forces and held in the spring receptacle. A single bake magnet may suffice, depending on the type of the spring. In the example, three permanent magnets which are disposed on top of one another are provided such that the effective length of the magnetic brake unit380corresponds to more than half the length of the spring receptacle430between the axial ends of the latter.

As a result of the retaining function of the magnets, the coil springs by using magnetic force are prevented from moving across comparatively large distances back in the direction of the exit opening such that the re-entry of springs from the exit side into the pipeline can be prevented to this extent.

The magnetic brake unit not only has a braking effect and a retaining effect on materials which are all originally magnetizable such as many spring wires, for example. The magnetic brake unit can in fact also be used effectively when processing coil springs from stainless steel, for example, thus in springs made from austenitic corrosion-resistant steel. As is known, this material has a very low magnetization capability and is practically non-magnetic in the production state. However, we established that the material becomes magnetizable when cold-formed by spring coiling. When using a magnetic brake unit, this can be utilized advantageously in the context of reliable deceleration and securing in relation to jumping out of the spring receptacle.

The automatically closing supply nozzle370described above is a passive construction element, the functions of the latter (deceleration by friction, blocking in relation to re-entry of a rebounding coil spring) in part being activated by the coil springs passing through per se. There are also examples of supply nozzles having a positive control, thus of externally switchable variants. To this end,FIG.7shows an example of a supply nozzle390which can be pneumatically externally actuated to immediately reduce the passage cross section as soon as a coil spring has completely exited the nozzle in the direction of the spring receptacle. Formed to this end in the nozzle mounting398is an annular duct396which by way of an air connector397can be connected to a compressed air source. In a manner similar to the example ofFIG.6, the supply nozzle has a sleeve-shaped closed base portion, and attached thereto elastic fingers or fins392, respectively, the free ends of the latter enclosing the exit opening395. In the absence of external forces, this exit opening395has a passage cross section which is slightly larger than the maximum external diameter of the coil spring such that the latter fits through without displacing the fingers toward the outside. At best, a minor or no braking effect is generated in this way. In the externally switchable example, the transport speed of the springs can be lower than in the self-closing exit nozzle described above because the springs do not have to “push” their own way through the nozzle.

An elastic sleeve391encloses the portions below the base portion, including the integral hinges and the fins or fingers, respectively, following therebelow. The supply sleeve in the non-stressed state is open so wide that the spring can fly through. Once the spring has flown through, the elastic sleeve391is impinged with compressed air. The pressure in the annular gap396has the effect that the elastic sleeve391is radially compressed. As a result, the fingers392of the nozzle are compressed to the extent that a rebounding spring can no longer enter the nozzle through the exit opening395. The air pressure is switched off for the next cycle such that the elastic sleeve and the fingers of the nozzle can assume their original shape again.

The system100(manufacturing system100) is equipped with an operating control system comprising a multiplicity of sensors to monitor the production and feedback-controlling production parameters as a function of sensor signals. Some of the sensors in the example are: a spring passage sensor S1in the initial region of the pipeline310in the proximity of the spring coiling machine200; a spring passage sensor S2-1in the end region of the pipeline310ahead of the beginning of the braking track. A further spring passage sensor S2-2in the proximity of the sensor S2-1, likewise ahead of the entry to the brake installation350. Sensors S3, S4and S5on the pipeline315which leads from the ejection station470-3for good parts to the downstream plant500. A sensor S6which detects the ejection of bad parts of a corresponding ejection station470-1. A sensor S7which checks the ejection of coil springs that are to be directed to quality control (Q). A sensor S8for counting potential coil springs which are ejected only at empty checking.

Furthermore provided are a plurality of nozzles by way of which compressed air can be fed into the pipelines at various locations. A nozzle D1is provided in the region of the spring suction device320; the nozzle D1causes the original acceleration of the severed coil springs F into the pipeline310. Because the pipeline can be relatively long, one or a plurality of intermediate acceleration nozzles can be expedient between the spring machine and the exit opening375on the downstream machine400; an intermediate nozzle D2is schematically illustrated. An intermediate acceleration nozzle D3(or a plurality of intermediate acceleration nozzles) can be provided also in the further pipeline315which is disposed downstream of the downstream machine400.

During operation, the sensor signals of the sensors S1and S2-1at the beginning and at the end of the pipeline310are utilized for monitoring the time-of-flight. If the latter is outside a permissible time-of-flight range, or if the latter will predictably develop from a still acceptable range to a critical range, for example, after a comparatively long operation by virtue of increasing contamination in the interior of the pipe, the volumetric flow of the compressed air in the suction installation320at the suction nozzle D1can be increased to ensure a time-of-flight in the specified range, for example.

The sensors S3, S4, and S5in the further pipeline can be utilized to monitor the time-of-flight. The signals can be processed in an analogous manner for controlling the intermediate nozzle D3to ensure that the conveyed coil springs arrive at the downstream plant500in the desired cycle of production of the coil springs.

The entry speed of the coil springs when entering the directly following brake installation350can be determined with the aid of the sensors S2.1and S2.2which lie close to one another. In the example a proportional valve, which controls the supply of compressed air at the intermediate nozzle D2, is activated as a response to target value variances outside the specified range.

Monitoring of the whereabouts of 100% of the springs can be carried out with the aid of the sensors S6, S7and S8when interacting with S5.