EP2708324B1 - Table top for the spring support table of a spring end grinding machine and spring end grinding machine with the same - Google Patents

Description

BACKGROUND

The invention relates to a table top for a spring support table of a spring end grinding machine according to the preamble of claim 1 and a spring end grinding machine equipped with at least one such tabletop according to the preamble of claim 9, (see, eg DE-C-883414 ).

Helical compression springs are machine elements that are required in numerous applications in large numbers and different designs. Helical compression springs are needed for example as suspension springs or valve springs in large quantities in the automotive industry. A helical compression spring may be described as a coiled or wound compression spring of wire with spaces between turns.

Of particular importance for the reliable function of helical compression springs in the intended use are the spring ends, ie, the two axial end portions of the helical compression springs.

The spring ends are used to transfer the spring force to the connector body and are usually designed so that at each spring position as axial as possible compression is effected. The spring end grinding, i. the material-removing machining of the spring ends by means of grinding, contributes in this context to create at the spring ends at right angles to the spring axis sufficient contact surfaces for the connection body.

Spring end grinding is part of the process chain for producing a helical compression spring from cold-formed wire. This process chain includes many further production steps, which ultimately lead to a ready-to-install helical compression spring.

For spring end grinding, the double side plan grinding process with unstressed springs has become established in many areas. When grinding with a rotating tool is known to be a machining process with geometrically indeterminate cutting. The designation of the double side grinding process depends on the type of surfaces to be created (flat surfaces), the number of surfaces to be ground (two), the mainly engaged part of the grinding wheel (side surface) and the process (grinding). A special feature of this method is the fact that the helical compression springs apply the grinding pressure itself.

A numerically controlled spring end grinder suitable for the double side grinding method has a grinding unit, a loading unit with a spring support table, and a control unit for controlling the loading unit and the grinding unit. The grinding unit has a grinding wheel pair with two vertically superposed rotatable grinding wheels, the axes of rotation are usually arranged coaxially to each other or slightly tilted against each other. Between the mutually facing side surfaces of the grinding wheels a grinding space is formed.

Adjacent to the grinding unit of the spring support table is arranged. A table top of the spring support table has on the side facing the grinding wheels a circular arc-shaped recess which is adapted to the outer edge of the lower grinding wheel so that only a narrow gap remains between the table top and the grinding wheel. The table top is mounted so that the top of the table top is located substantially level with the abrasive top surface (side surface) of the bottom grinding wheel. A tabletop can be constructed in one piece or in several parts from a plurality of matching tabletop segments

The loading unit has at least one loading plate shaft, which is provided for receiving a loading plate. There are single-bed machines that can hold only a single loading plate, and multi-table machines that have two or more loading plate shafts. In single-layer machines, the loading plate is always in a working position in which the loading and unloading takes place. Multi-table machines often have a turntable which is rotatable about a vertical turntable axis. The turntable carries at least two axially parallel with the turntable axis rotatable loading plate shafts, which are each provided for receiving a loading plate. A table top of the turntable can act as a movable table top segment of the table top of the spring support table. The loading plates received by the loading plate shafts can be transported away from the grinding unit by rotating the turntable between a working position in the vicinity of the grinding unit and a loading position. At the same time as the grinding operation, the loading plate located in the loading position can be loaded and / or unloaded. The turntable thus allows a grinding process with low auxiliary times for loading and unloading and thus high productivity.

During a grinding operation, those helical compression springs, which are accommodated in spring housings of the loading plate arranged in the working position, are transported by rotation of the loading plate successively on a circular arcuate sliding track or track through the grinding space between the rotating grinding wheels. In each case, both spring ends of the helical compression springs located in the grinding space are simultaneously processed by grinding. Outside the grinding space, the helical compression springs run in continuation of the grinding path on an arcuate spring track on the spring support table and are based on the top of the table top of the spring support table from.

In order to keep the transition between the grinding room and the spring support table or between the spring support table and the grinding room as smoothly as possible, we in the DE 883 414 proposed to provide in the table top of the spring support table particular, relative to the table top on a circular path slidable support plates with annular section-shaped or segmental shape. For example, made of hardened steel massive support plates can be clamped from its lateral edge to the table top by means of claws. After loosening the clamp, it is possible to adjust by circular arc-shaped displacement of the support plates the arcuate gap to the adjacent grinding wheel so that regardless of any existing diameter differences in the grinding wheels used only a minimal gap remains and thus always a trouble-free transition even with springs with small diameters occurs when entering the grinding room and the exit from the grinding room.

To achieve a long service life, tabletops for spring support tables or the associated tabletop segments are manufactured today from through-hardened steel. Are the tabletops or tabletop segments worn out, they are removed and replaced with new ones. The preparation of such table tops is relatively expensive, the removal and installation relatively expensive and thus also expensive for the end user.

TASK AND SOLUTION

It is an object of the invention to provide a table top for a spring support table of a spring end grinder which, viewed over the useful life of a spring end grinder, is less expensive for the end user than conventional table tops. Furthermore, it is an object to provide a low-maintenance, low-maintenance spring end grinder.

To solve this problem, the invention provides a table top for a spring end grinding machine with the features of claim 1 and a spring end grinding machine with the features of claim 7 ready.

Advantageous developments are specified in the dependent claims. The wording of all claims is incorporated herein by reference.

Generic table tops according to the claimed invention have a layer structure at least in a transition region adjoining the circular arc-shaped recess. This layer structure or this layer structure is characterized in that a relatively thick support plate is provided and on the support plate, a cover layer is provided which is thin relative to the support plate, which is connected flat to the support plate and has a free surface which the free surface of the table top forms. The carrier plate consists of a first material. By contrast, the top layer consists of one in comparison to the first material significantly more wear-resistant second material. Thus, a composite structure is created whose components are made of different materials, each of which can be selected independently according to their function.

An essential function of the carrier plate is to give the tabletop sufficient mechanical stability. For this purpose, the carrier plate can be, for example, several centimeters thick and consist of a suitable steel material (first material). A backing plate may have a continuous flat top that supports the cover over its entire area. The relatively thin cover layer, which forms a laminar composite with the stable support plate itself does not require high mechanical stability, since the mechanical stability is created by the surface bond with the solid support plate. Thus, the material for the cover layer (the second material) can be selected for the least possible wear in the mechanical stress during spring end grinding.

The thickness of the cover layer may be relatively small and, for example, 10 mm or less, in particular 5 mm or less. The thickness can e.g. between 1 mm and 5 mm, e.g. at about 4 mm.

Sometimes the thickness of the cover layer is at most 40% or at most 20% of the thickness of the support plate. The thickness of the cover layer may be e.g. between 1% and 15% of the thickness of the support plate, if necessary, above.

If the table top is or will be composed of two or more table top segments, the layer structure may be provided at one, several or all table top segments, at least at Tabletop segments (one or more) immediately adjacent to the recess.

Due to the layer structure of the table top or of table top segments at least in the transition region adjacent to the recess, there are functional and economic advantages.

During the grinding process, the springs, which are received in a loading position located in the working position, move in a circular orbit about the axis of rotation of the loading plate. The springs run again and again from the spring support table via an inlet area into the grinding space between the grinding wheels and after a short time of processing again in an outlet area on the spring support table. Outside the grinding space, the lower spring ends move in a loop on the surface of the spring support table in a circular arc before being transported again into the grinding space. As a result, the surface of the spring support table, especially in the inlet area and in the outlet area close to the grinding space mechanically stressed, which leads to signs of wear due to abrasion of material.

Nevertheless, in order to achieve the highest possible service life of the table top, these have traditionally been made of through-hardened steel. If the tabletops or the particularly heavily used tabletop segments are worn, they are completely disposed of and replaced with new ones. This procedure is relatively expensive for the user. It also wastes resources. In addition, the installation of a new table top or a new table top set is usually quite expensive, so that machine downtime results and decreases the productivity of spring end grinding.

The invention can alleviate these problems. By selecting suitable wear-resistant second materials for the cover layer, the wear problem can be significantly mitigated, so that an exchange of table tops or table top segments less often than previously necessary. In addition, it is no longer necessary to manufacture the entire carrier plate of through-hardened, relatively wear-resistant material. The support plate may for example consist of an unhardened steel material and is thereby cheaper to manufacture, since no effort for curing and no effort for the elimination of any problems curing, such as hardening distortion or cracks must be driven. Thus, on the one hand longer life and on the other hand lower manufacturing costs.

In some embodiments, the cover layer has a self-supporting thin cover plate, which may for example have the shape of a thin sheet. Typical thicknesses of cover plates may range between 3 mm and 8 mm, e.g. at 4 to 5 mm.

According to the invention, the cover plate is releasably connected or connectable to the carrier plate, so that an exchange of the cover plate is easily possible. The cover plate may be connected to the support plate e.g. be braced flat with the help of screws and / or other clamping means. A surface connection by gluing is possible, but the replacement is then usually more expensive.

On the one hand to produce a reliable surface connection between the cover plate and carrier plate and on the other hand not intended to interfere with the intended for contact with the spring ends top of the table top, the cover plate according to the invention by means of acting on the back of the cover plate clamping devices is braced flat with the support plate. At the Cover plate, for example, be welded on the back bolts that reach through recesses in the support plate, so that a tension of the composite of the back of the support plate is possible.

In some embodiments, the cover plate is made entirely of the wear-resistant second material. The cover plate can be formed for example by a suitably designed piece of wear plate, as it is commercially available, for example, under the brand name HARDOX ^® . Sufficient wear resistance or abrasion resistance is found to be the case with second materials having a Brinell hardness of at least 350 HBW, the hardness in particular being between 350 HBW and 500-600 HBW. The use of other wear-resistant materials, such as plastic or ceramic or composites with it is possible.

Cover plates, which consist entirely of a wear-resistant second material, can be reworked if necessary after a correspondingly long service life by regrinding and continue to be used.

It is also possible that a cover plate itself has a multilayer structure. For example, it can be provided that the cover plate has a base plate which has a wear-resistant coating on its upper side (facing away from the carrier plate). The base plate can then consist of a material of lower wear resistance than the coating, for example of unhardened steel. The wear resistant coating, in some embodiments, is a cemented carbide coating that may be applied to the base plate, for example, in a flame spraying process.

In some embodiments, the table top is composed of a plurality of table top segments, each of the table top segments having a carrier plate segment and a cover plate segment mounted thereon. Preferably, a cover plate segment has a slightly larger surface area than the associated carrier plate segment, so that the cover plate segment projects beyond the carrier plate segment on at least one lateral edge region around a projection. If such table top segments arranged to form a larger table top directly next to each other, then only the mutually facing side edges of adjacent cover plate segments abut each other, while leaving a greater distance between the associated side edges of the underlying support plate segments. With this configuration, it is possible to create a composite of several tabletop segments table top, adjacent table top segments can be joined virtually seamlessly, so that serving as a spring support surface table surface practically unbroken acts in the joints for all practical purposes. It takes advantage of the fact that certain separation processes for cutting plate segments can work with higher precision if the material thickness to be cut is relatively thin. Thus, it is possible to produce the cover plates geometrically very precisely, for example by laser cutting or water jet cutting, while it is possible to work with the carrier plate segments with higher tolerances, without thereby impairing the quality of the table surface.

If necessary, the layer structure with the support plate and the cover layer can be supplemented by a further thin plate, which can be used, for example, as a matching plate for leveling after regrinding a wear plate. The further thin plate can, for example, on the side facing away from the cover layer of the support plate be arranged between the support plate and a substructure of the spring support table. It can thereby be achieved that the carrier plate and a cover layer applied thereon, for example in the form of a wear plate, can remain joined together as a related unit and only have to be separated again when the wear plate has to be finally replaced. For regrinding, the entire unit with support plate and cover layer can be removed and reground on a grinding machine. The loss of total thickness can be compensated by inserting a suitable balance plate. In principle, it is also possible to provide an intermediate plate between the carrier plate and a cover plate.

The invention also relates to a spring end grinding machine for grinding spring ends of helical compression springs, wherein the spring support table of the spring end grinding machine has a table top of the type described in this application.

These and other features will become apparent from the claims and from the description and drawings, wherein the individual features each alone or more in the form of sub-combinations in one embodiment of the invention and in other fields be realized and advantageous and protectable Can represent versions. Embodiments are illustrated in the drawings and are explained in more detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1

shows a schematic side view of a spring end grinding machine according to an embodiment of the invention;

Fig. 2

shows a plan view of the spring support table of the spring end grinding machine Fig. 1 ;

Fig. 3

shows a diagonal perspective view of the composite of several tabletop segments table top of the spring support table in Fig. 2 ;

Fig. 4

shows a section along the section line IV-IV in Fig. 2 ;

Fig. 5

shows an oblique perspective view of a single table top segment of the table top; and

Fig. 6

shows a sectional view of the area of a butt joint between two adjacent tabletop segments of the table top.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, particular aspects of embodiments of the invention using the example of a vertically constructed spring end grinder 100 are shown, which is set up for the dry processing of helical compression springs (also referred to as springs) in the double-side plan grinding process with unstressed springs in the delivery process. The machine is built in single construction with two grinding spindles and two loading plates. It essentially comprises a grinding unit 120, a loading unit 150 and a control unit 125 for controlling controllable components of the loading unit 150 and the grinding unit 120.

To the loading unit includes a spring support table 190 with a table top 200, which has a flat surface 202, which is the free surface of the Forming spring table. In the Fig. 2 in plan view and in Fig. 3 Table top shown in perspective is composed of seven tabletop segments 210, 220, 230, 240, 250, 260, 270, which adjoin each other along narrow butt joints virtually seamlessly and together form a substantially closed planar surface.

The grinding unit 120 has a single grinding wheel pair with two coaxially rotatable grinding wheels 130, 140, between which a grinding space 135 is formed during operation of the machine. The upper grinding wheel 130 is fixed to the lower end of an upper grinding spindle 132, which is mounted with a vertical axis of rotation 134 in the upper part of the support structure of the grinding unit and can be driven by an upper motor 136. The lower grinding wheel 140 is supported by a lower grinding spindle 142 rotatably mounted in the lower part of the support structure, which can be rotated by a lower motor 146 about a vertical axis of rotation 144 which is coaxial with the axis of rotation 134 of the upper grinding spindle.

The height-variable grinding space is bounded upward by the side surface 131 of the upper grinding wheel 130 substantially perpendicular to the rotation axis 134 and the lower grinding wheel side surface 141 oriented substantially perpendicular to the lower rotation axis 144. This abrasive side surface 141, that is the upper side of the lower grinding wheel, should preferably be at the same height as the free surface 202 of the spring loading table 200.

The upper functional unit with upper grinding spindle 132 and motor 136 is height-adjustable for adaptation to different spring lengths. The lower grinding spindle can be moved vertically. In embodiments that are also used for the spring end grinding in a continuous process is provided as an option to bring one of the grinding wheels or one of the grinding spindles in a defined skew. In order to be able to carry out a grinding process in the feed process, the upper grinding spindle 132 can be delivered by movement parallel to the spindle axis 134 in the direction of the lower grinding wheel, wherein the feed rate or the delivery speed profile can be predetermined by the control unit 125.

The loading unit 150, which is arranged directly next to the grinding unit 120, has two loading plates 160, 170, which can rotate indefinitely with the grinding wheels and are jointly supported by a turntable 180, which can be rotated indefinitely by a motor about a vertical axis of rotation 182. The turntable 180 is a movable part of the spring support table 190.

A total circular table top of the turntable is composed of two semicircular table top segments 210, 220. These form a rotatable inner region of the table top of the spring support table 200. The outer table top segments 230 to 270 form a ring around this rotatable inner region and are fixedly mounted on a horizontal plate 192 of a substructure of the spring support table. At the grinding wheels 130, 140 side facing the table top 200 has a circular arc-shaped recess 215, which is adapted to the outer edge of the lower grinding wheel 130 of the grinding unit so that between the table top 200 and the closest to the grinding wheels arranged table top segments 230, 240th and the radial edge of the lower grinding wheel 130 remains only a narrow arcuate space.

The first loading plate 160 is supported by a first loading plate shaft 162, which is mounted with vertical axis of rotation 164 on the turntable.

The first loading plate is located in Fig. 1 and Fig. 2 in its working position with partial engagement in the grinding room. The second loading plate 170 is supported by a second loading plate shaft 172 which is rotatable about a vertical axis of rotation 174. The axes of rotation of the loading plates are at equal radial distances from the axis of rotation 182 of the turntable at diametrically opposite positions. The second loading plate is in its loading position, which allows a mechanical or manual loading and unloading of the spring retainers. The loading plates are each easily interchangeable to set up the machine for different spring geometries.

Each loading plate has a plurality of off-axis to its axis of rotation arranged spring receivers 166, each to receive a single helical compression spring for processing. Helical compression springs generally have a cylindrical shape, other shapes such as tapered shapes, convex or concave double-cone shapes or cylindrical shapes with tapered spring ends are possible. Spring housings can be used with and without spring boxes. One-storey or multi-level loading plates can be used. In the embodiment, the loading plates are one-story and have spring receptacles in three different radial distances from the axis of rotation of the loading plate. The spring mounts are arranged in three concentric rings or rows around the axis of rotation (see. Fig. 2 ).

In the representations of the Fig. 1 and 2 the first loading plate 160 is in its working position with partial engagement in the grinding space, while the second loading plate 170 is in the loading position. In the working position of the center distance between the center of rotation of the grinding wheels, ie their axes of rotation, and the axis of rotation 164 of the loading plate is dimensioned so that all spring retainers upon rotation of the loading plate about its axis of rotation on a circular arc slideway or track through the grinding space between the rotating Grinding wheels are transported. During this rotational movement, the two opposite spring ends of the helical compression springs located in the grinding space are each simultaneously ground by the side surfaces of the grinding wheels coming into contact therewith. The achievable removal rate is essentially determined by the position of the track of the individual helical compression springs in the grinding space, by the grinding speed, the loading plate speed and the grinding pressure generated at the respective machined surfaces.

Outside the grinding space 135, the helical compression springs run in continuation of the grinding path on an arcuate spring track over the spring support table 200 and are based on the upper side 202 of the table top of the spring support table. Here, the lower spring ends rub under the weight of the springs on the table surface. A certain material removal by the frictional stress is unavoidable, so that in the course of the useful life, especially along the circular-arc spring courses in the workstation, ie on the table plate segments 230 and 240 of the spring inlet and the spring outlet results in abrasive wear on the table surface.

The negative consequences of this wear are mitigated in embodiments of the invention by a special layer structure or a layer structure of the table top 200 and the associated table top segments 210 to 270. The tabletop or its tabletop segments are constructed in sandwich construction. This is especially good in Fig. 4 to recognize which a vertical section along the section line IV-IV in Fig. 2 shows. The substructure of the spring support table closes upwards with a fixed, horizontal, solid plate 192, which rests on vertical wall elements of the substructure. This horizontal plate carries in the illustrated area the ring segment-shaped Tabletop segment 270, which is part of the fixed outer ring of the spring support table. The tabletop segment 270 has a solid support plate 272 made of unhardened steel material whose thickness is several centimeters. On the flat top of the support plate segment 272 facing away from the plate 190, a cover plate 274 which is thin in comparison to the support plate is stretched flat with a thickness of a few millimeters, so that the support plate and the cover plate form a solid, flat composite.

Under the support plate 272 may be a further thin fitting plate 278, which compensates for the regrinding of the cover plate or wear plate 274 with the appropriate thickness removed at the wear plate during regrinding measure. In other embodiments, such a plate may be missing.

The cover plate can be replaced relatively easily. To clamp the cover plate releasably on the support plate, projecting at the back of the cover plate at suitable positions of the back threaded studs 276 are welded, which engage in the correct position applied cover plate by stepped through holes in the support plate. For flat clamping of the cover plate with the support plate hex nuts 279 are screwed onto the protruding threaded bolt sections and tightened from the back of the support plate. As a result, an easily removable at any time, solid surface conditions between the support plate and cover plate is created. The attachment of the weld studs on the back of the cover plate ensures that the opposite side of the cover plate, which forms the free surface 202 of the table top, can remain intact and free of perforations. The strained composite of support plate and cover plate is then screwed by means of clamping screws 194 on the plate 190 of the substructure, wherein the clamping screws through the plate 190 through threaded holes in the back of the support plate engage.

A corresponding sandwich structure or layer structure with clamping device and exchangeable cover plate segment is provided in all tabletop segments of the table top.

The carrier plate or the carrier plate segment 272 is made of relatively soft, unhardened structural steel. This material is available at low cost and can be precisely machined without any special effort. The thin cover plate 274 consists of a suitably cut by means of laser cutting or water jet cutting piece of a wear plate made of a hardened steel material having a Brinell hardness of about 400 HBW. Suitable wear plates are commercially available for example under the trademark HARDOX ^®. Such wear plates get their extraordinary hardness by quenching in a water bath, so that despite a low content of alloying materials, a high hardness and an associated wear resistance can be achieved. At the same time weldability is given, so that the clamping bolt 276 can be reliably attached to the back by welding.

In the embodiment shown, all table top segments 210-270 have the same layer structure or the same sandwich construction with self-supporting, and if necessary easily replaceable, wear-resistant cover plates which completely cover the underlying support plates.

The sandwich construction of the individual tabletop segments or the entire tabletop not only has advantages in terms of the service life of the table top, but also manufacturing advantages. One aspect we use the FIGS. 5 and 6 explained in more detail. Fig. 5 shows the tabletop segment 230, which on its side facing the lower grinding wheel has a part 215 'of the circular arc-shaped recess 215 for adaptation to the outer grinding wheel contour. Opposite, a rectilinear side edge 236 is cut, which should abut directly on a correspondingly rectilinear side edge 256 of the cover plate 254 of the adjacent table top segment 250 when the table top is assembled. In the Fig. 5 visible inner, concavely curved, arcuate edge is directly adjacent to the inner rotatable part of the table top, formed by the table top segments 210 and 220 in assembled table top.

The arranged below the wear-resistant cover plate 234 solid support plate 232 is kept slightly smaller on all sides than the cover plate 234 thereon, so that the cover plate or the cover plate segment projects laterally by a small protrusion (typically at most 1 to 2 mm on the underlying side edge of the support plate Also, the adjacent cover plate 254 protrudes slightly beyond the support plate segment 252. Due to the relatively small thickness of the cover plate material, when cutting the cover plate segment by laser processing or water jet cutting, for example, the desired side edge can be produced with high accuracy fit accurately that in the area of the resulting butt joints 255 (see. Fig. 6 ) Gap widths at most in the order of 100 microns, so that the table surface 202 acts substantially uninterrupted.

Since the edges of the carrier plates are set back against these significant side edges, it is not necessary to work with such great accuracy when cutting the carrier plate. These carrier plates can also be cut out, for example, by laser or by means of a water jet. The higher tolerances when lasers or water jets Of thicker plates play in this way afterwards in the assembly of the entire tabletop no longer matter.

There are many variations possible. In a non-illustrated embodiment, a removable from the support plate cover plate is also provided. However, this is not consistently made of a wear-resistant second material, but has itself a layer structure by on a base plate, which does not have to consist of a wear-resistant material, and, for. may consist of unhardened steel, a wear-resistant coating, for example by flame spraying is applied. It may be, for example, a hard metal coating. The advantages of easy disassembly of the composite of carrier plate and cover plate are retained.

In other embodiments, only the tabletop segments particularly affected by wear in the inlet region and outlet region of the springs, ie those tabletop segments that correspond to the segments 230 and 240, provided with a wear-resistant cover layer, possibly also the tabletop segments that close the turntable upwards.

When worn, only the upper wear plates or cover plates are replaced. These can be produced very cost-effectively, since they can already be lasered out of hard material (eg HARDOX®) and otherwise require no further processing. The wear plates can be reground if necessary. The thickness loss can be compensated by compensating plates of appropriate thickness in the layer composite. The complex assembly of solid support plates is eliminated, since only the cover layer must be replaced. It consumes significantly less material than conventional tabletops, since the carrier plates or carrier plate segments can be used again and again.

The variant with carbide coating offers a significantly increased wear resistance compared to conventional table tops.

For tabletops or tabletop segments in sandwich construction (support plate or support plate segment mounted thereon cover plate or cover plate segment) only the upper, usually a few millimeters thick and cost-effective available part, namely the wear plate, replaced. If necessary, this can be reground once or even several times to extend the life of the arrangement. The carrier plate or a carrier plate segment can always be preserved. Any loss of height that may result from regrinding can be compensated by interposing a compensating plate of suitable thickness between the substructure and the support plate and / or between the support plate and the cover plate.

By coating the table segments affected particularly by wear in the inlet region and outlet region of the springs in the immediate vicinity of the arcuate recess by means of carbide or another, wear-resistant material, the life of the tabletops or tabletop segments can be significantly extended.

Coated tabletops or tabletop segments may also be sandwiched or solid construction. As a further advantage in addition to the higher stability, it may turn out that the base material of the support plate or a base plate, which is then coated with cemented carbide or another wear-resistant material, itself does not have to be cured. A coating can take place over the whole table top segment or over the entire tabletop or only partially in the transition area the incoming and / or outgoing springs are performed.

Preferred embodiments have been explained with reference to the example of a Mehrtellerkaschine with two loading plates and turntable. The invention can also be used in Eintellermaschinen that can accommodate only a single loading plate.

Claims (13)

1. Table top (200) for a spring support table (190) of a spring end grinding machine (100) for grinding spring ends of helical compression springs, wherein the spring end grinding machine includes a grinding unit (120) having two vertically superimposed rotating grinding wheels (130, 140), with a grinding cavity (135) provided between them, and a spring support table (190) of a loading unit (150) disposed adjacent to the grinding unit, wherein
   the table top (200) includes a circular arc-type recess (215) on a side assigned to the grinding wheels, the recess being matched to the outer rim of a lower grinding wheel (140) of the grinding unit such that not more than a small intermediate space remains between the table top (200) and the grinding wheel,
   characterized in that
   the table top (200) includes, at least in a transition zone adjacent to the recess, a layer structure with a support plate (232) and a covering layer (234) disposed on the support plate and thin as compared to the support plate, said covering layer being in a two-dimensional connection to the support plate and having a free surface which constitutes the surface (202) of the table top,
   wherein the support plate is composed of a first material and the covering layer is composed of a second material more wear-resistant as compared to the first material, and
   wherein the covering layer includes a self-supporting thin cover plate (274, 234, 254) detachably connected to the support plate (272, 323, 252),
   wherein the cover plate (274) is in a two-dimensional bracing connection to the support plate (272) by means of clamping devices (276, 279) engaging on the rear side of the cover plate.
2. Table top according to claim 1, characterized in that the cover plate (274, 234, 254) is composed completely of the second material, wherein the second material is preferably a hardened steel material.
3. Table top according to claim 1, characterized in that the cover plate includes a base plate provided with a wear-resistant coating, in particular a hard metal coating, on the top side facing away from the support plate.
4. Table top according to any of the preceding claims, characterized in that the support plate is composed of a non-hardened steel material.
5. Table top according to any of the preceding claims, characterized in that the table top is assembled from a plurality of table top segments (210 to 270), wherein each of the table top segments includes a support plate segment and a cover plate segment applied thereon, wherein preferably a cover plate segment (234, 254) has a slightly greater surface area than the associated support plate segment (252, 232), so that the cover plate segment protrudes beyond the support plate segment at least in a lateral rim portion by a projecting length.
6. Table top according to any of the preceding claims, characterized in that on a side of the support plate (272) facing away from the covering layer (274) another plate (278) is disposed and arranged between the support plate (272) and a substructure (192) of the spring support table, when the spring support table (190) is in the installed condition.
7. Spring end grinding machine (100) for grinding spring ends of helical compression springs, comprising:

   a grinding unit (120), including a pair of grinding wheels having two vertically superimposed rotating grinding wheels (130, 140), with a grinding cavity (135) provided between them,

   a spring support table (190), disposed adjacent to the grinding unit and having a table top (200) which includes a circular arc-type recess (215) on a side assigned to the grinding wheels, the recess being matched to the outer rim of a lower grinding wheel (140) of the grinding unit such that not more than a small intermediate space remains between the table top and the grinding wheel,

   characterized in that

   the table top includes at least in a transition zone adjacent to the recess (215) a layer structure with a support plate (232, 252, 272) and a covering layer (234, 254, 274) disposed on the support plate and thin as compared to the support plate, said covering layer being in a two-dimensional connection to the support plate and having a free surface which constitutes the surface (202) of the table top,

   wherein the support plate (232, 252, 272) is composed of a first material and the covering layer (234, 254, 274) is composed of a second material more wear-resistant as compared to the first material, and

   wherein the covering layer includes a self-supporting thin cover plate (274, 234, 254) detachably connected to the support plate (272, 323, 252),

   wherein the cover plate (274) is in a two-dimensional bracing connection to the support plate (272) by means of clamping devices (276, 279) engaging on the rear side of the cover plate.
8. Spring end grinding machine according to claim 7, characterized in that the cover plate (274, 234, 254) is composed completely of the second material, wherein the second material is preferably a hardened steel material.
9. Spring end grinding machine according to claim 7, characterized in that the cover plate includes a base plate provided with a wear-resistant coating, in particular a hard metal coating, on the top side facing away from the support plate.
10. Spring end grinding machine according to any of claims 7 to 9, characterized in that the support plate is composed of a non-hardened steel material.
11. Spring end grinding machine according to any of claims 7 to 10, characterized in that the table top is assembled from a plurality of table top segments (210 to 270), wherein each of the table top segments includes a support plate segment and a cover plate segment applied thereon, wherein preferably a cover plate segment (234, 254) has a slightly greater surface area than the associated support plate segment (252, 232), so that the cover plate segment protrudes beyond the support plate segment at least in a lateral rim portion by a projecting length.
12. Spring end grinding machine according to any of claims 7 to 11, characterized in that on a side of the support plate (272) facing away from the covering layer (274) another plate (278) is disposed and arranged between the support plate (272) and a substructure (192) of the spring support table, when the spring support table (190) is in the installed condition.
13. Spring end grinding machine according to any of claims 7 to 12, characterized in that it includes a loading unit (150) having a rotary table (180) rotating about a vertical rotary table axis (182),
    wherein the rotary table carries at least two rotatable loading tray shafts (162, 172) axially parallel to the rotary table axis and each shaft provided for receiving a loading tray (160, 170),
    wherein the loading trays received from the loading tray shafts are transportable by turning the rotary table (180) between a working position in the vicinity of the grinding unit (120) and a loading position remote from the grinding unit, and
    wherein a table top of the rotary table is part of the table top of the spring support table.

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