Grinding machine for spiral springs

Abstract

 Grinding machine for spiral springs comprising a rotating table, a shaft driving said rotating table rotatably about the axis thereof, a pair of grinding wheels rotating about a common axis thereof, one or more horizontal sliding surfaces carrying the springs, a hub provided under said rotating table and supporting said shaft; the machine is provided with both horizontal adjustment means, which are adapted to selectively and continuously determine the distance between said driving shaft of the rotating table and the axis of rotation of said grinding wheels, and vertical adjustment means, which are adapted to selectively determine in a continuous manner the height of said rotary driving shaft relative to said sliding surfaces.

Description

[0001] The present invention refers to an improved kind of grinding machine for spiral springs, which is particularly flexible in its utilization scope to cater for the great variability in the types of springs to be ground and the grinding wheels.

[0002] Spiral springs, and in particular the springs that are designed to work as compression springs, are largely known to be generally submitted, during the manufacturing thereof, to a grinding operation at the extremities or end portions thereof, so that such end portions show, during use, respective planar surfaces, and these planar surfaces are parallel to each other and orthogonal to the axis of the spring spiral.

[0003] The machines used to perform this grinding operation on spiral springs in general, and compressively operating spiral springs in particular, are generally described in the patent publication EP 0722810 B1, which reference should therefore be conveniently made to. The grinding machines described in this publication are essentially characterized in that they are able to provided with grinding-wheel types that may differ even to a considerable extent from each other, in accordance with the actual kind of processing required and the type of spring to be ground.

[0004] This possibility for the grinding machine to be appropriately set up in accordance with each single mode of utilization thereof, i.e. each single particular application it is intended for, ensures a satisfactory operative flexibility of the same machine; however, it has been found in practice that, under the working conditions that commonly exist in a usual industrial ambient, there tend to show up some drawbacks that put the possibility for these machines to be used in an optimum manner in jeopardy.

[0005] In particular, these drawbacks may be summarized as follows:

• In the first place, since the centre-to-centre distance between the rotary driving shaft of the spring-carrying table and the two grinding wheels arranged thereabove is fixed, when the spring-carrying table is replaced it may occur that - for reasons shall not be investigated here any closer, since scarcely relevant to the purposes of this discussion - some error or undesired variation in the diameter thereof is introduced.
  Such possible variation - although of a modest extent - has an effect on the wear-off pattern of the grinding wheels since, if the grinding wheel and the spring-carrying table are in the relative arrangement shown in Figure 2A, an uneven wear-off pattern will generate in the grinding wheel , owing to the latter working solely in the area outside the circle "A", so that in correspondence to such circle a step "S" - as best shown in the enlarged detail view appearing at a side of the same Figure - is formed, which must then be removed, i.e. levelled off separately through an additional grinding operation.
  Obviously, for each condition of distance existing between the two axes X and Y, the optimum situation occurs in the way as this is exemplified in Figure 2.
  The need may furthermore well arise for rotating tables having different diameters to be desirably installed and used, but this would not be allowed practically by the machine, owing to the rigidity of the geometry thereof.
• A second drawback depends on the fact that, as anyone is well aware of in the art, when the springs to be ground have a changing diameter of the coiled wire (but a constant, i.e. unchanged height thereof), the need arises for the distance between the spring-carrying table and the sliding surfaces to be properly adjusted, i.e. adapted. It is in fact largely known that the thicker a wire is, the greater shall the distance between the sliding surface and the spring-carrying table be, in view of regularly enabling the wire to protrude by an extent equal to almost a diameter thereof from the lower plane of the spring-carrying table.

[0006] Currently, the adjustment of the height of the spring-carrying table relative to the sliding surfaces and, hence, to the structure of the machine, is performed by removing the spring-carrying table, inserting some annular, i.e. ring-like members around the driving shaft of the table and, finally, putting back the same table in place.

[0007] However, these operations generally prove quite unhandy to carry out, due to the limited space available therearound, while things are made still worse by the fact that the tables themselves are heavy and bulky, so that several operators are generally required to handle them conveniently.

[0008] Ultimately, therefore, a rather extended machine downtime is generally required, along with an intensive use of labour, whenever the height of the spring-carrying table requires being adjusted.

[0009] A third drawback arises when, for operational reasons, the need arises for the spring-carrying table to be replaced. Currently, when such need arises, the table itself must of course be first lifted in order to enable it to slip and be taken off the vertical driving shaft thereof. This involves a handling that, further to invariably proving quite delicate and fatiguing to carry out, generally lacks accuracy, several attempts having usually to be made in view of inserting the new table onto the related driving shaft. This operation is particularly demanding and awkward to carry out, due also to the fact that a table has in all cases a certainly not negligible weight, so that it is almost invariably the cause of easily understandable inconveniences and a significant waste of time, especially when the tables need be replaced rather frequently.

[0010] It would therefore be desirable, and it is actually a main purpose of the present invention, to provide a grinding machine for spiral springs, which is provided with means adapted to enable the centre-to-centre distance between the axis of the driving shaft of the spring-carrying table and the axis of the grinding wheel to be adjusted in a continuous manner, as well as means adapted to enable the height of the spring-carrying table to be adjusted, again in a continuous manner, relative to the sliding surfaces, and hence relative to the structure of the machine, along with means adapted to enable the height of the driving shaft to be adjusted in accordance with the number and the position of the tables that are to be associated thereto.

[0011] According to a further purpose of the present invention, the machine of the above-specified kind shall be capable of being manufactured with the use of means and devices that are both reliable and low-cost, as well as readily available on the market, shall be competitive in its construction and, furthermore, shall not entrain any significant alterations in the general performance capabilities or any reduction in the reliability thereof.

[0012] According to the present invention, these aims as set forth above, along with further ones that will become apparent from the following description, are reached in a grinding machine made so as to incorporate the features and characteristics as recited in the appended claims.

[0013] Features and advantages of the present invention will anyway be more readily and clearly understood from the description that is given below by way of non-limiting example with reference to the accompanying drawings, in which:

• Figure 1 is a simplified perspective view of an open grinding machine, in which both the spring-carrying table and the two grinding wheels are clearly visible;
• Figures 2 and 2A are respective symbolical see-through views of two possible mutual positions of the rotating table and the grinding wheels according to the prior art;
• Figure 3 is a front elevational view of the portion below the rotating table in a grinding machine according to the present invention;
• Figures 4 and 5 are respective top plan sectional views along the section plane V-V of Figure 3, in an assembling phase and in an as assembled state, respectively;
• Figure 6 is a symbolical perspective view of the machine parts shown in Figure 5;
• Figures 7 and 8 are respective axial plan sectional views of the portion illustrated in Figure 3, in two different operating arrangements thereof;
• Figure 9 is a top view of the rotating table provided with an improvement according to the present invention;
• Figure 10 is a view of a central portion of the table and the driving shaft along the section line C-C in Figure 9;
• Figure 11 is a diagonal perspective top view of the assembly shown in Figure 9;
• Figures 12 and 12A are respective views of a couple of advantageous embodiments of the inventive driving shaft;
• Figures 13 and 14 are an exploded view and a view in an assembled state, respectively, of a different embodiment of the driving shaft according to the present invention.

[0014] With reference to Figures 1, 2 and 3, a grinding machine according to the prior art comprises:

• a common base or structure 1 of the machine,
• a circular rotating table 2, which is shown symbolically with a dashed line 101, at the periphery of which there is provided one or more lines of holes 3 arranged in a circle-like pattern around the central axis of said table 2,
• a rotating or driving shaft 4 extending through a central bore 5 of said rotating table 2 and sharing the same axis X as said rotating table,
• a pair of grinding wheels 6, 7 arranged each on a respective one of the two faces of said table and adapted to be driven rotatably about a common axis Y that is parallel to said axis X;
• one or more sliding surfaces 8, 9 arranged partially below said rotating table 2 and mainly in the zone that is not occupied by the lower grinding wheel 6, so that the springs 10 contained in the respective holes 3 are prevented from falling off said holes as they move along their path prior to reaching, i.e. being intercepted by the lower grinding wheel 6.

[0015] Furthermore, underneath said rotating table there is arranged a small circular resting surface 12 adapted to support said table 2, which is appropriately bored at its centre, said rotating or driving shaft 4 rising coaxially from said resting surface to pass through said central bore 5 in sad table.
   According to a first aspect of the present invention, and with reference to Figure 1 illustrating a grinding machine in its open state (in the sense that the assembly formed by the sliding surfaces, the shaft, the hub, etc., has been moved away, through a limited rotation about a pin, from the pair of grinding wheels), the hub 11 accommodates a portion of the driving shaft 4, which juts out both upwards, so as to engage the spring-carrying table, and downwards to connect with driving means M (shown in a mere symbolical manner in the Figure) used to drive said shaft rotatably.

[0016] This hub 11 is coupled rigidly to a plate 13 by means of one or more brackets 14 (see Figures 3, 6), whereas this plate 13 is in turn coupled rigidly to one or more properly shaped slides 15 adapted to be inserted in and slide on respective horizontal runners 16 provided in the edge 17 of the structure 1 of the machine that is oriented towards said hub.

[0017] From this same edge there protrudes an integral relief 18 which, when said shaped slides 15 are inserted in the respective runners, penetrates the space existing within said brackets 14 (see Figure 5).

[0018] In said brackets 14 and said integral relief 18 there are provided respective mutually aligned holes 14A and 18A; the hole 18A is threaded, whereas the holes 14A are not threaded.

[0019] Finally, a correspondingly threaded screw 19 is inserted between said holes 14A, relative to which it is then able to turn freely, and 18A; in addition, in correspondence to one of said holes 14A there are provided retaining means 50 (shown symbolically in the Figures), which are adapted to prevent said threaded screw 19 from being able to slip axially relative to the holes 14A provided in said brackets 14.

[0020] Those skilled in the art will at this point be fully able to readily realize the way in which the inventive device works: all it takes, in fact, is to act on said threaded screw 19 and this screw, owing to its having its threads engaging the threaded hole 18A, i.e. the relief 18 connected to the structure of the machine, acts in turn upon the brackets 14 and, hence, the plate 13, thereby causing said shaped slides 15 to slide along said horizontal runners 16.

[0021] Since these runners are provided in the edge 17 of the machine structure, and since the brackets 14 are connected to the hub 11, it will be readily appreciated that, with the above-described operation, the hub 11 itself is at the same time caused to displace as desired relative to the same machine structure 1 and, along with the hub 11, also the shaft 4, supported by the same hub, will be displaced accordingly.

[0022] Of course, anyone skilled in the art will at this point be fully capable of properly selecting the size, the geometry and the orientation of the various parts and members relative to each other so as to obtain the desired direction of displacement. In a preferred manner, this will be such as to ensure that, with a simple operation performed on said screw 19, the resulting displacement is effective in causing said axis X of the hub, and therefore of the shaft contained therein, to move closer to/away from the axis Y of said grinding wheels along a straight line "r", as this is shown symbolically in Figure 4.

[0023] As far as the vertical adjustment of the height of the rotating table 2 relative to said sliding surfaces 8 and 9 is concerned, reference should now be made to Figures 7 and 8.

[0024] These Figures basically illustrate a median vertical sectional view of the assembly comprising the rotatably driving shaft, the rotating table and the hub. In these illustrations, the hub 11, connected to the structure of the machine by means of said brackets 14, can be noticed to contain a cylindrical sleeve 20 thereinside.

[0025] This cylindrical sleeve is in turn coupled to the rotatably driving shaft 4, onto which the rotating table 2 is resting, by means of one or more ball bearings whose axes are coaxial with the rotatably driving shaft 4. A body 24 of such ball bearing is coupled rigidly to the outer cylindrical surface of the rotatably driving shaft 4, whereas the other body 25 is coupled to a corresponding inner surface of the sleeve 20.

[0026] In turn, the sleeve 20 is coupled to said hub 11 by means of a threaded cylindrical coupling 22 provided between the outer surface of the sleeve and a corresponding inner cylindrical portion of the hub 11. Finally, on a different outer portion of said sleeve, which is however accessible from the outside, there are provided some holes 23 (see also Figure 6) adapted to be engaged by a suitable tool (not shown) in order to be caused to rotate about the axis X.

[0027] Basically, the weight of the rotating table 2 relieves, i.e. discharges itself onto said circular resting surface 12 and, from here, onto the rotatably driving shaft 4; from the latter, via the bearings 21, it then discharges itself onto the sleeve 20 and, via the threaded coupling 22, the hub 11 that is ultimately connected to the structure 1 of the machine by means of said brackets 14.

[0028] As it can be readily inferred, the whole arrangement works as follows: when the height of said rotating table is to be varied, an operator has just to insert said tool (not shown) in said holes 23 of the sleeve and act on these holes so as to cause the same sleeve to rotate in the desired rotation.

[0029] Since said sleeve is coupled, via said threaded coupling 22, to said hub 11 that is unable to rotate since firmly joined vertically with the machine, the sleeve itself will displace vertically relative to the hub. Owing to the sleeve being coupled vertically to the rotatably driving shaft by means of the ball bearing 22, it ensues that the same shaft is therefore raised/lowered, thereby causing also the small circular resting surface 12, firmly joined thereto, and ultimately even the rotating table supported by, i.e. resting upon said circular resting surface 12 to displace accordingly.

[0030] As far as the problem connected with the replacement of the rotating table is concerned, along with the operative difficulties deriving therefrom, an advantageous solution lies in following improvement: with reference to Figures 9, 10 and 11, the rotating table 2 is provided with a central bore 30 having a diameter that is significantly larger than the diameter D0 of the rotatably driving shaft 4 (see Figure 10). In this manner, the same rotating table can be inserted on the shaft without any difficulty or insecureness.

[0031] However, this would not ensure that the table sits perfectly centered on this shaft, so that, in view of obtaining the required centering effect, there is provided an adapter ring 31, provided internally with a through-bore 32 of a cylindrical shape and having a diameter that is slightly larger than the outside diameter of the rotatably driving shaft.

[0032] Such adapter ring is shaped outwardly in the form of a disk and is subdivided into two contiguous, cylindrical portions 33, 34 that are coaxial with the axis X of the shaft.

[0033] The lower portion 33 has an outside diameter D1 that is just slightly smaller than the diameter of said central through-bore 30 provided in the rotating table for said shaft to pass therethrough, whereas the upper portion 34 has a diameter D2 that is larger than the diameter of the bore 30 and, hence, the diameter D 1.

[0034] For the rotating table to become duly centered on the shaft, all it takes therefore is to apply said adapter ring from the head portion of the shaft and let id slide downwards until it comes into contact with the table 2. The desired centering of the table is then obtained by adjusting the position of the same table manually, until the latter eventually takes such a position as to enable said adapter ring to spontaneously fall with its lower portion 33 exactly into said central bore 30, thereby automatically holding the table securely in that perfectly centered position.

[0035] Since said adapter ring is self-centering , owing to the diameter of the through-bore 32 thereof being sized to the diameter of the shaft, it practically ensues that the rotating table, which is at this point centered around said adapter ring, turns out as being automatically centered also relative to the axis of the shaft.

[0036] On the other hand, owing to the rotatably driving shaft being further provided with a side key 35 to engage the table 2 and move it rotatably (in a manner that is largely known as such in the art, actually), it will be readily appreciated that even said adapter ring must have a correspondingly shaped contour so as to avoid interfering with such key 35. It is however advantageous if just an angular portion is cut away or, anyway, removed from said adapter ring, so as to further simplify the shaft-to-adapter ring coupling, without any undesired interference.

[0037] Anyway, the possibility still exists for a further improvement to be introduced: in fact, the need arises in a number of cases for springs having a very reduced height to be processed; in these cases, there is no need for a very high rotatably driving shaft to be available, since this shaft only needs to be just as high as actually required to rotatably drive the rotating table.

[0038] In a number of other cases, however, the springs to be processed are very high, so that not a single rotating table, but rather several rotating tables 2A, 2B, 2C need to be used duly arranged above and spaced from each other, as this is illustrated symbolically in Figure 12.

[0039] In this cases, therefore, the rotatably driving shaft needs to be adequately high in view of being able to both support and rotatably drive all said tables.

[0040] In order to cope with both these requirements, the above-mentioned improvement calls for said shaft to be made as a plurality of individually low-height segments 36, 37, 38, etc., having the same diameter.

[0041] If these segments are coupled together by arranging them upon each other in a stack, so as this is illustrated in Figures 13, 14 and 15, they aggregate to form a rotatably driving shaft of a selectively variable height, according to actual needs, whereas just a single one of these segments, i.e. the lower one, is installed if only a single rotating table is used, with the advantage that no need arises for a heavy rotating table to be lifted to an excessively high position in order to be able to apply it onto the driving shaft from above the - unnecessarily too high, in this case - head portion of the same shaft.

[0042] These segments are advantageously capable of engaging each other either by means of suitable mutual coupling means 41, 42 (see Figure 13) or, as an alternative, by means of a single fastening member, preferably a bolt 43, which can be inserted from above and, acting as a tie-bolt, clamps and secures the top segment 45 against the support base of the lower rotating plate, so as shown in Figures 12 and 14. thereby automatically fastening at the same time all possible intermediate segments in the desired position.

Claims

1. Spring grinding machine (1), comprising:

- a circular rotating table (2), along the periphery of which there are provided one or more lines of holes (3) arranged in a circle-like pattern around the central axis of said rotating table (2),

- a shaft (4), which drives said rotating table (2) rotatably about the axis (X) thereof,

- a pair of grinding wheels (6, 7) arranged each on a respective one of the two opposite faces of said table and adapted to be driven rotatably about a respective axis (Y) that is parallel to, but distinct from said axis of rotation (X),

- one or more sliding surfaces (8, 9) adapted to support the springs (10) within their respective holes (3) they move along their path prior to reaching, i.e. being intercepted by the lower grinding wheel (6),

- a hub (11), which is arranged below said rotating table (2), and which bears, even indirectly, said shaft (4),

- driving means (M) adapted to drive said shaft and said pair of grinding wheels rotatably about the respective axes (X, Y) thereof,

characterized in that it is further provided with horizontal adjustment means adapted to selectively adjust in a continuous manner the distance (d) of said axis of rotation (X) of the rotating table from the axis of rotation (Y) of said grinding wheels (6, 7).

2. Grinding machine according to claim 1, characterized in that said horizontal adjustment means comprise:

- at least a horizontally sliding member (15) adapted to displace in a direction parallel to said distance (d) relative to a portion (17) of the structure of the machine, and engaging a runner portion (16) of the same structure,

- at least a rigid linking member (14) between said hub (11) and said horizontally sliding member (15),

- one or more adjustment screws (19) arranged between respective holes (14A) of said rigid linking member (14) and respective adjustment holes (18A) provided either in said portion (17) of the machine structure or, as an alternative thereto, in at least a relief (18) provided integral with or firmly joined to said portion (17) and protruding therefrom, said screw (19) engaging said adjustment holes (18A) by the meshing of respective corresponding threads and being freely rotatable relative to said holes (14A) of the rigid linking member (14),

- retaining means (50) that are adapted to prevent said screws (19) and said rigid linking member (14) from displacing axially relative to each other.

3. Grinding machine according to the preamble of claim 1, characterized in that it is provided with vertical adjustment means adapted to selectively adjust in a continuous manner the height of said rotatably driving shaft (4) of said rotating table relative to said hub (11).

4. Grinding machine according to claim 3, characterized in that said vertical adjustment means comprise:

- a sleeve (20) surrounding the lower portion of said shaft coaxially thereto, and inserted inside said hub (11),

- cylindrical threaded means (22) enabling a portion of the outer surface of said sleeve to engage a corresponding portion of the inner surface of said hub,

- at least a ball bearing, which supports said shaft (4) vertically, and which is applied with a body portion (25) thereof firmly joined to the same shaft and with another body portion (24) thereof firmly joined to said sleeve (20).

5. Grinding machine according to claim 1, characterized in that it is provided with centering means adapted to automatically ensure bring the rotating table (2) into centering relative to said rotatably driving shaft thereof.

6. Grinding machine according to claim 5, characterized in that said centering means comprise:

- an adapter ring (31) provided with a central through-bore (32), the inside diameter of which is such as to ensure a clearance-free fitting onto said shaft (4), and which is formed by two distinct, coaxial ring portions (33, 34) arranged contiguously upon each other,

- in which the upper portion (34) has an outside diameter (D2) that is larger than the diameter (D1) of the lower portion (33), said diameter (D1) of the lower portion being adapted to be inserted in the bore (30) of said rotating table (2) under establishment of a self-centering coupling.

7. Grinding machine according to any of the preceding claims, characterized in that said shaft comprises a plurality of separate cylindrical segments (36, 37, 38) capable of being stacked upon each other.

8. Grinding machine according to claim 7, characterized in that, said separate, stackable segments (36, 37, 38) may be linked with each other in pairs by means of a plurality of mutual engagement means (41, 42) provided on the respective contiguous faces thereof.

9. Grinding machine according to claim 7, characterized in that, said separate, stackable segments (36, 37, 38) are firmly secured all together to said rotating table by means of an elongated fastening means, preferably a tie-bolt (43), connecting the head portion of the upper segment to said rotating table.

Drawing