WO1996033047A1

WO1996033047A1 - Lapping machine

Info

Publication number: WO1996033047A1
Application number: PCT/EP1995/001477
Authority: WO
Inventors: Herbert Pickelmann
Original assignee: MESSERSCHMIDT, Jürgen
Priority date: 1995-04-19
Filing date: 1995-04-19
Publication date: 1996-10-24

Abstract

A lapping machine of the horizontal type for balls has an approximately circular, rotary lapping wheel (3) and an opposite fixed lapping wheel (2) coaxially arranged to the rotary lapping wheel (3). Both lapping wheels (2, 3) are provided on their circular face with concentric grooves for receiving the balls to be lapped. The axis (20) of the lapping wheels (2, 3) is slightly inclined in relation to the vertical. The balls (6) are led from a magazine (7) into the grooves (5) through a segment-shaped recess (4) in one of the lapping wheels and return to the magazine (7) after leaving the grooves (5). This lapping machine is characterized in that the fixed lapping wheel (2) is arranged below the rotary lapping wheel (3) and has the segment-shaped recess (4), and in that the balls (6) are transferred between the lapping wheels (2, 3) and the magazine (7) from below through the segment-shaped recess (4). The advantage of this lapping machine is that the balls are led into the lapping grooves and returned into the magazine by gravity, so that their surface is not damaged.

Description

Lapping machine

DESCRIPTION

The invention relates to a lapping machine of horizontal design for balls.

The need for balls, especially for ball bearings, is immense. Many millions of ball bearings are currently produced daily; the amount of balls required for this is correspondingly high.

The series of production steps described below has recently proven to be optimal for the production of such balls.

For the production of rolling bearing balls, the starting point is an appropriately dimensioned wire, which is unwound from a roll and divided into correspondingly long cylindrical pieces with the aid of a machine. Subsequently, the cylindrical wire piece is received in a two-part spherical die, which is pressed together under high force so that an approximately spherical structure is formed. However, the spherical structure obtained in this way still has gross geometry errors.

These rough geometry errors are roughly leveled on the still soft workpiece in the following manufacturing step; this production step is called flashing, deburring or grinding.

The next manufacturing step is a heat treatment. The previously soft workpieces are hardened and then tempered. The spheres present at this stage are, however, in general in both their dimensional accuracy and not sufficient in terms of surface quality either. For this reason, several processing steps follow, which include, for example, grinding and fine grinding.

All of the processing steps described so far are already known, so that further discussion is unnecessary.

The final dimensional accuracy and surface quality is achieved by lapping the balls in one or more stages. In this production step, an abrasive is loosely added to the cooling medium, which is then correctly referred to as a "lapping suspension".

The machines for lapping balls that are common today and known to date can in principle be differentiated according to two types, the main distinguishing feature of which relates to the spatial arrangement of the lapping disks. Basically, these lapping disks can be arranged both horizontally and vertically.

In a lapping machine of horizontal design, the two lapping disks are thus arranged horizontally. One of the lapping disks is rotated by a motor or the like, while the other lapping disk is arranged coaxially with it and is stationary. The opposite circular surfaces of these two disks are provided with concentric grooves which are approximately circular segment-shaped in cross section and can accommodate a large number of balls. The non-rotating lapping disk is subjected to an axially directed force, so that when the lower lapping disk rotates, the balls located in the grooves are forced to undergo a continuous circular rolling motion, during which the lapping process takes place or the ball surfaces are machined.

The number of balls that can be processed in a lapping process is naturally small. In order to combine a much larger number of balls into one processing batch, the known lapping machines are usually used equipped with a bullet magazine. The balls are guided from the ball magazine to the lapping machine, processed there, conveyed back into the ball magazine and processed again after a certain period of time.

Such a ball magazine can be designed, for example, as an annular trough which is arranged around the lapping disks. This magazine is slowly rotated against the direction of rotation of the lapping disks. In order to enable the balls in the ball magazine to be continuously exchanged with the balls located between the lapping disks, the upper lapping disk has a segment-shaped recess. The balls in the ball magazine are transported through the self-rotation of the magazine with the aid of various guide mechanisms into the segment-shaped recess of the upper lapping disk. There they are distributed over the concentric grooves of the lower lapping disk. The rotational movement of the lower lapping disk forces the balls between the two lapping disks so that the lapping process can take place. After the balls have almost completely circulated between the two lapping disks, they reach the segment-like recess of the upper lapping disk again. There they are lifted out of the groove of the lower lapping disk by specially shaped lifting mechanisms or the like and fed back into the ball magazine. There they remain with the ball magazine rotating continuously until they reach the guiding mechanisms again and are processed again. This process continues until the balls have reached the desired final dimension.

The lapping machine of horizontal design has the advantage of a relatively even rolling motion of all balls involved, since the weight of the balls does not accelerate or brake them. The disadvantage of the lapping machine of horizontal design, however, is that a certain force has to be exerted on the balls both when they are introduced into the lapping grooves and when the ball is removed from these lapping grooves by a lifting tool or the like. This results in the finest damage to the Ball surface, which has an adverse effect on the ever increasing quality requirements for high-quality ball bearings. Balls for low-noise ball bearings in particular require all possible surface damage to be avoided.

In the known vertical type lapping machine, the lapping disks are arranged vertically. In this case too, one lapping disk is rotated by a motor, while the other lapping disk is stationary and thus does not rotate. With this type of construction, the segment-shaped recess is also located in the non-rotating lapping disk. This segment-shaped recess is oriented horizontally in order to facilitate the exchange of balls with a ball magazine. With this type of construction as well, the balls in the magazine can be lifted out of the magazine groove by the rotation of the magazine against guide mechanisms or the like, and with the help of the balls that follow, and transported into the segment-shaped recess of the non-rotating lapping disk, where they are concentric Grooves of the rotating lapping wheel can be distributed. The rotating movement of the rotating lapping disk forces the balls between the two lapping disks, so that the lapping process can take place. After the balls have reached the segment-like recess of the non-rotating lapping disk again after an almost complete revolution between the two lapping disks, they are guided back into the ball magazine by guide plates or the like. There they remain with the ball magazine rotating continuously until they meet the guide mechanisms again and are reinserted between the lapping disks. This process is continued until the balls have reached the desired final dimension.

The lapping machine of the vertical type has the advantage that the balls can be fed and removed more easily than in the lapping machine of the horizontal type, since the gravity of the balls can be exploited both during feeding and during removal. As a result, it is possible to damage the ball by means of feed devices and to reduce lifting devices. Nevertheless, such damage is not completely avoided.

The main disadvantage of the lapping machines of vertical design is that the gravity of the balls can both brake and accelerate the kinematically forced movement during machining. This effect is particularly noticeable when the balls to be machined differ slightly in diameter. The slightly smaller balls do not come into contact with the lapping disks and therefore withdraw from the kinematically provided rolling motion. For this reason, they have to be pushed by subsequent, slightly larger balls. This becomes particularly problematic if the ball has reached the bottom dead center of the circular lapping groove after entering the lapping grooves and then opposes movement resistance on the way to the top dead center of the subsequent ball. This often leads to the surfaces of the balls being damaged in such a way that they have to be classified as qualitatively inferior or become completely unusable. In addition, a lifting tool is also required in the lapping machines of a vertical type, which lifts each individual ball out of the lapping grooves after it has rotated in order to convey them into the ball magazine. Here, too, there is the danger of causing minimal surface damage to the ball.

Attempts have now been made to combine the advantages of the lapping machines of horizontal and vertical design. For example, in lapping machines of a horizontal design, the lapping disks have been slightly inclined. In other words, the axis of rotation of the lapping disks is slightly inclined with respect to the vertical. A lapping machine of this type is described in German patent 834 815 and in German additional patent 964 028.

A lapping machine of the latter type is also described in international application WO 88/08771 (international application number PCT / HU 88/00032). In both known lapping machines of horizontal design with inclined lapping disks, the segment-like recess is still in the upper lapping disk, which is fixed while the lower lapping disk is being rotated. The balls are thus still inserted from above into the lapping grooves between the lapping disks. Therefore, guiding mechanisms and lifting tools are still required, which can damage the balls.

It is therefore an object of the present invention to provide an improved lapping machine of a horizontal type with inclined lapping disks in which the balls are not damaged both during insertion between the lapping disks and during removal.

This object is achieved by a lapping machine of horizontal design for balls with an approximately circular, rotating lapping disk and a fixed lapping disk, which is located opposite and coaxially on the end face, both lapping disks being provided with concentric grooves on their front circular surface for receiving the ball to be machined and the axis of the lapping disks is inclined with respect to the vertical, and with a ball magazine from which the balls are guided into the grooves through a segment-shaped recess in one of the lapping disks and into which the ball is returned after exiting the grooves, which thereby is characterized in that the fixed lapping disk is arranged below the rotating lapping disk and has the segment-shaped recess, and that the exchange of the balls between the lapping disks and the ball magazin from below through the segment-shaped recess in the bottom fixed lapping disc.

In the lapping machine according to the invention, the lapping disks are arranged essentially horizontally, so that the weight of the balls does not interfere with the kinematically forced rolling movement of the lapping. As a result, no movement resistance is opposed to the subsequent balls. In addition, the friction between the balls is reduced so that it does not become surface-destructive seizure phenomena, as can occur with the lapping machines of vertical construction.

In the lapping machine according to the invention, the lapping disks are arranged essentially horizontally. However, they are slightly inclined. In other words, the axis of rotation of the

Lapping disks (more precisely the rotating lapping disk) form a small angle with the vertical. The non-rotating lapping disk provided with the segment-shaped recess is arranged below the closed, rotating lapping disk. The balls are thus guided from below through the segment-shaped recess to the lapping grooves; after the balls have emerged from the lapping grooves, the balls are guided downwards through the segment-shaped recess. In the lapping machine according to the invention, therefore, no tools are required to insert the balls into the lapping grooves or to lift the balls out of the lapping grooves. All insertion and lifting operations are carried out with the help of the gravity of the balls, so that the balls are not subjected to any constraining forces that could affect their surface.

The invention is explained in more detail below with reference to the drawings. From the drawings show:

1 shows the arrangement of the two lapping disks of the lapping machine according to the invention without the ball magazine in a view from below,

2 is a side view, partly in section,

3 shows a perspective view of the essential components of a lapping machine according to the invention, including the ball magazine.

Fig. 4 Another embodiment of a ball magazine and

Fig. 5 is a schematic representation of the essential details of a ball feed. In Fig. 1, the lower, non-rotating lapping disk is provided with the reference number 2. This lapping disk 2 has a segment-shaped recess 4 through which the rotating upper lapping disk 3 lying above it is partially visible. Both lapping disks 2, 3 are provided on the circular surfaces facing each other in a known manner with grooves 5 for receiving the balls 6 to be machined. The upper lapping disk 3 rotates in the direction of rotation shown (arrow). The balls 6 to be machined are fed to the lapping grooves 5 at the inlet edge 8 and then leave them again at the outlet edge 9.

With the help of the side view shown in FIG. 2 and the perspective view shown in FIG. 3, the running of the balls 6 through the machine, including the ball magazine, can be described. A single considered ball 6 is located at the leading edge 8 and is conveyed by the rotation of the upper lapping disk 3 into the lapping groove 5, where it is transported further due to the rolling kinematics until it leaves the lapping groove 5 at the trailing edge 9 again. Following its own gravity, it then falls into the trough 10 of the ball magazine 7, whereby it may be corrected beforehand in its falling movement by the guide plate 11. Since the ball 6 leaves the lapping groove 5 only due to its own gravity, a special lifting tool can be dispensed with. This eliminates the risk of fine surface damage from such a tool. The ball 6 is now transported by the slow rotation of the ball magazine 7, whereby it increases in height. The ball magazine 7 has a slowly rotating bottom and outer part 12 and a fixed inner part 13, which together form an annular groove 10. In the vicinity of the upper point, the balls 6 located in the ball magazine 7 pass through an opening 14 in the stationary inner part 13, so that they fall out of the ball magazine 7 towards the inside due to their own gravity. The fall

Balls 6 on a guide plate 15, which is directed and slightly inclined so that the balls 6 are returned to the leading edge 8. So that gravity can be used, the lapping disks 2, 3 are arranged slightly inclined. In other words, the axis 20 of the lapping disks encloses a small angle α with the perpendicular.

The plane of the ball magazine 7 in which the channel 10 rotates is also slightly inclined. Thus, the axis of rotation 21 also has a small angle β to the vertical.

The mounting of the lapping disks 2, 3, the mounting of the rotating lapping disk 3, the devices for rotating the lapping disk 3 and the ball magazine 7 can be conventional and known per se and are therefore not shown in the figures for the sake of clarity. The mechanisms for adjusting the distance between the two lapping disks from one another and for applying pressure are also of a known type and are therefore not shown. In the lapping machine according to the invention, the upper, rotating lapping disk 3 is expediently pressurized.

4 shows a further exemplary embodiment of a ball magazine 7. In this case, the ball magazine 7 has a one-piece, annular groove 10, in which both the bottom 16 and the two side walls 17 and 18 rotate equally. In this case, the balls remain in the ball magazine 7 for a three-quarter rotation, as a result of which the magazine's filling quantity is still significantly increased. The ball guide plate 11 is designed so that it dips into the circular ball magazine 7, so that the balls in the ball magazine 7 are pushed onto the ball guide plate 11 by the self-rotation of the ball magazine 7, from where they are then under the influence roll into the lapping grooves with their own gravity.

5 shows in a special and schematic manner the transition of the balls from the guide plate 11 into the lapping grooves of the lower lapping disk 2. In the lower area, this guide plate 11 is designed such that the balls are guided in running grooves which spread out in a fan shape, so that they are placed on the leading edge 8 directly in front of a lapping groove, without first hitting the web between two lapping grooves and having to find its way into a lapping groove under the action of forces which are forced on by the upper, rotating lapping disk 3. For this purpose, elements 19 are mounted on the guide plate 11 for fanning out the ball flow. In a further embodiment, the lower part of the guide plate is spatially designed or shaped in such a way that the flat, upper region merges into a fanned lower region, which finally has only discrete treads which only take up individual balls one after the other can, the flow of the individual balls moving one behind the other then being directed directly onto a lapping groove. This ensures that the balls are kept away from surface-destroying influences.

In order to optimally utilize the system-related advantage of largely excluding the gravity of the balls during the lapping process, the aim is to have the lapping discs 2, 3 as small as possible in relation to the horizontal or the smallest possible angle α between the vertical and the axis of rotation 20 of the lapping disc 3 . The in the

The indicated inclination of the lapping disks 2, 3 and the ball magazine 7 is clearly exaggerated for reasons of clarity in the illustration. The inclination angles of the axis of rotation 20 of the lapping disk and the axis of rotation 21 of the ball magazine 7 do not have to be identical, although this is preferred. An identical inclination of these axes of rotation 20, 21 leads to advantages in the manufacture of the lapping machine.

In the figures, the segment-shaped recess 4 is shown such that it has an opening angle of the fixed one

Lapping wheel 2 corresponds to 90 °. However, this numerical value is only to be understood as an example, from which, depending on the design requirements, there can also be significant deviations. In principle, the opening angle should be kept as small as possible in order to achieve the longest possible lapping path and thus also the most effective lapping process possible.

Claims

PATENT CLAIMS

1. Lapping machine of horizontal design for balls with an approximately circular, rotating lapping disk (2) and a stationary, opposite and coaxially arranged lapping disk (3), both lapping disks (2, 3) on their end circular surface for receiving the balls to be machined (6) are provided with concentric grooves (5) and the axis (20) of the lapping disks (2, 3) is inclined with respect to the vertical, and with a ball magazine (7) from which the balls (6) pass through a segment-shaped recess ( 4) are guided into the grooves (5) in one of the lapping disks (2, 3) and into which the balls (6) are returned after exiting the grooves (5), characterized in that the fixed ones Lapping disk (2) is arranged below the rotating lapping disk (3) and has the segment-shaped recess (4) and that the balls (6) are exchanged between the lapping disks (2, 3) and the ball magazine ( 7) from below through the segment-shaped recess (4).

2. lapping machine according to claim 1, characterized in that the ball magazine (7) is designed such that the emerged from the grooves (5), in the ball magazine (7) fallen balls (6) by own movement of the Kugelmaga¬ interest (7) gain in height, fall out of the ball magazine (7) and be fed back into the grooves (5) with the aid of a guide plate (11) using gravity.

3. Lapping machine according to claim 1 or 2, characterized in that the ball magazine (7) represents an annular groove (10) which rotates about an axis of rotation (21) inclined with respect to the vertical.

4. Lapping machine according to claim 3, characterized in that the inclination of the axis (20) of the lapping disks (2, 3) and the axis of rotation (21) of the ball magazine (7) is the same.

5. Lapping machine according to claim 3 or 4, characterized in that the ball magazine (7) and the lapping disks (2, 3) rotate in opposite directions.

6. Lapping machine according to one of claims 2 to 5, characterized in that the guide plate (11) fans out into individual ball grooves, which guide the balls (6) located thereon exactly into a lapping groove (5).