Lapping or Polishing Machine

When working with a rotating lapping wheel or a rotating polishing wheel, differences are often caused in the stressing of the working face due to differences in the lapping speed, differences in the distribution of lapping mixture, and differences in the pressure per unit of area. As a result there is an unequal distribution of temperature over the lapping wheel. Consequently, the predetermined shape of the working face may change undesirably. The quality of the workpiece is then detrimentally influenced both by the different temperature and also due to the deformation of the lapping wheel. Many lapping tasks can be carried out only with a specific lapping wheel temperature.

It is known to provide lapping wheels with a chamber or with a plurality of inter-connected chambers through which a fluid flows which discharges all the surplus heat of the lapping wheel. It has been found that when using that system more particularly in the case of large lapping wheels, the working face of the lapping wheel cannot be kept at the same temperature in all regions if the temperature produced by the lapping work differs at different regions of the working face.

An object of the present invention is to keep the working face of the lapping wheel at the same temperature in all regions under any lapping stressing.

According to the present invention this object is achieved by a plurality of zones of that face of the lapping wheel which is opposite from the working face of the said wheel, comprising separate supply ducts for fluids at different temperatures and/or rates of throughflow, a temperature sensor for each zone of the working face which corresponds to one of the afore-mentioned zones, said temperature sensors being connected with a device for controlling the temperature or the throughflow rate of the fluid.

Preferably that face of the lapping wheel which is opposite from the working face comprises a plurality of annular recesses each having an inlet and an outlet for the fluid. These recess are preferably connected with their own conduit which leads to its own annular groove of a part rotating with the drive shaft of the lapping wheel.

The same arrangements according to the invention can also be provided in the case of polishing machines.

The invention is described hereinafter with reference to a constructional example of a lapping machine with an annular shape of the lapping wheel.

FIG. 1 shows a vertical section taken on the line I--I of FIG. 2,

FIG. 2 shows a view from below of the lapping wheel of FIG. 1,

FIG. 3 shows a plan view of the larger-diameter portion of the drive shaft.

The illustrated lapping machine has a lapping wheel 1 which is in the form of a circular disc and whose rear side is secured by means of screws 19 on a supporting flange 2, which can be rotated by a shaft 4 by means of a motor 5 by way of a transmission 6. The shaft 4 comprises a portion 7 of somewhat larger diameter which is mounted in a bearing 3 supporting by means of a ball bearing 3a the supporting flange 2.

The rear side 1" of the lapping wheel 1 comprises four recesses 1a,1b,1c,1d which are in the form of concentric annular grooves interrupted at a location u. One end of these annular grooves is connected to a conduit 8a,8b,8c,8d respectively and the other end to a conduit 9a,9b,9c,9d respectively. The conduits 8a to 8d lead to annular grooves 16a to 16d of the portion 7, whilst the conduits 9a to 9d lead to annular grooves 17a to 17d of the portion 7. Externally the annular grooves are closed by the bearing 3. Conduits 15a to 15d lead to the annular grooves 16a to 16d; conduits 18a to 18d lead to the annular grooves 17a to 17d.

Provided above the horizontal working face 1' of the lapping wheel 1 is an arm 11 supporting four measuring elements 10a, 10b, 10c, 10d situated in each case above the recesses 1a,1b,1c,1d of the lapping wheel 1. These are measuring elements which ascertain the temperature of the working face 1' of the lapping wheel, for example on the principle of direct temperature measurement or measurement of a variation in length corresponding to the temperature variations. The measuring elements 10a to 10d are connected via lines 12 to a device 13 in which a fluid introduced through a feed conduit 14 is brought in separate quantities to different temperatures, which correspond in such a manner to the temperatures detected by the measuring elements 10a to 10d that when these quantities of fluid are supplied to the recesses 1a to 1d the temperature of the working face 1' of the lapping wheel is kept at the same level everywhere.

The device 13 connects with the recesses 1a to 1d via conduits 15a,15b,15c,15d and conduits 8a,8b,8c,8d. The conduits 15a to 15d extend through bores in the bearing body 3 and debouch there into peripheral grooves 16a,16b,16c,16d of the portion 7 of the drive shaft 4. Conduits 8a to 8d open into these grooves 16a to 16d, so that the fluid which has been brought in the device 13 to a temperature corresponding to the temperature ascertained by the measuring element 10a, in other words serves for compensating for the temperature of the working surface 1' of the lapping wheel, is supplied via the conduit 15a, the annular groove 16a and the conduit 8a to the recess 1a. In the same way, fluids which have been brought to the appropriate temperature by the device 13 are supplied to the recesses 1b,1c,1d by way of the conduits 15b to 15d, the annular grooves 17b to 17d and the conduits 8b to 8d. The fluids supplied to the recesses 1a to 1d are discharged via conduits 9a to 9d, annular grooves 17a to 17d and conduits 18a to 18d. In the case of the illustrated machine a polishing wheel can be used instead of a lapping wheel.

The lapping wheel can comprise appropriate cavities in its interior instead of recesses 1a to 1d which form chambers, closed after the lapping wheel 1 is placed on the supporting flange 2.

Instead of separate annular grooves 17a to 17d the portion 7 can comprise--besides the annular grooves 16a to 16d--a single annular groove into which all-the conduits 9a to 9d open, and then the discharge conduits 18a to 18d are replaced by a single conduit. The separate conduits 9a-9d can be replaced by a common conduit for returning the fluid from the compartments 1a-1d.