A rotatable drum having a plurality of receiving stations for loading workpieces to be processed is rotated about a horizontal central axis through a plurality of work stations including at least one blasting station and a loading and unloading station. Each receiving chamber forms a sealed blasting chamber in the area of the blasting process station and flow off of the blasting medium and the blasted particles occurs by an arrangement of flow off channels defined between each of the receiving chambers and connected with the chambers in a labyrinthine manner in the central area of the drum.

The present invention relates generally to workpiece processing apparatus 
and more particularly to a multiple station centrifugal blasting machine 
wherein workpieces are placed within receiving chambers of a rotating drum 
and moved through processing stations during operation of the apparatus or 
machine. 
A machine of the type to which the present invention relates is known in 
the prior art for example from U.S. Pat. No. 4,355,490 and in this machine 
flow off discharge or drainage of the blasting medium which is utilized 
for process blasting of workpieces and of particles which are blasted off 
the workpieces is not possible in every position of the workpiece 
receiving chambers of the machine. For this reason, in prior art machines 
of this type, two blasting stations are arranged in the lower area 
thereof. However, in this arrangement no blasting medium or other 
particles can flow off during tumbling of the workpieces which is effected 
in the loading and unloading stations of the equipment. 
Additionally, it is disadvantageous in that the loading and unloading 
stations arranged above will require a high construction cost and 
expensive loading devices in that the cycle or phase time is determined by 
the sum of the tumbling, unloading and loading times and in that different 
holding devices are required for the various kinds of workpieces because 
of the frontal face support or holding of the workpieces or the machine is 
not universal enough. 
Accordingly, the present invention is directed toward provision of a 
multiple station centrifugal blasting machine of the type discussed above 
wherein, despite compact construction and shorter processing times for the 
workpieces, there may be ensured a flow off of the blasting medium and of 
the blasted particles from each of the workpiece receiving chambers in 
each position of the apparatus so that there may be selected desirable 
positioning of the blasting process station or stations and of the loading 
and unloading stations. 
Additionally, the workpiece holding devices are constructed in such a 
manner that workpieces of various shapes and sizes can be securely 
supported within the receiving chambers without requiring specialized 
holding equipment in such a manner that abrasive blasting processes will 
be ensured on all sides. 
SUMMARY OF THE INVENTION 
Briefly, the present invention may be described as blasting apparatus for 
passing workpieces through a plurality of process stations comprising a 
drum having a generally cylindrical configuration defining a plurality of 
receiving chambers each adapted to receive therein workpieces to be 
processed, means for rotating said drum about a central axis thereof for 
passing said receiving chambers through a plurality of process stations 
including at least one blasting process station and a loading and 
unloading station, said blasting process station including means for 
directing a blasting medium at said workpieces within said receiving 
chambers and means defining in said drum between each of said receiving 
chambers thereof flow off channels extending radially of said drum for 
enabling outflow of said blasting medium, said flow off channels being 
connected with said receiving chambers in a labyrinthine manner in the 
central area of said drum. 
As a result of the apparatus of the invention it will be ensured during 
processing of the workpieces that the blasting medium and the particles 
blasted from the workpieces can flow off from each receiving chamber and 
in any position of the chamber. 
Thus, desirable positioning for each station, such as for example the 
blasting, tumbling and loading and unloading stations may thereby be 
arranged without difficulty thereby making it possible to provide a 
construction which is compact and easier to load. 
The various features of novelty which characterize the invention are 
pointed out with particularity in the claims annexed to and forming a part 
of this disclosure. For a better understanding of the invention, its 
operating advantages and specific objects attained by its use, reference 
should be had to the accompanying drawings and descriptive matter in which 
there is illustrated and described a preferred embodiment of the 
invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings, there is shown blasting apparatus in 
accordance with the present invention which essentially comprises a 
multiple station blasting process machine including a blasting housing 1 
wherein a drum conveyor 2 is arranged to as to be rotatable about a 
horizontal axis 3. The drum 2 is rotatably driven by means of a geared 
motor 4 and the drum is arranged to define four receiving chambers 5 which 
are uniformly distributed about the circumference of the drum 2. Each of 
the receiving chambers 5 is adapted to receive workpieces 6 which can be 
introduced in a stepwise manner cyclically through a loading and unloading 
station 7. The drum 2 is rotatable so that the receiving chambers 5 may be 
moved through a plurality of processing stations including the loading and 
unloading station 7, two blasting process stations 8 and 8a and a tumbling 
station 9 defined within the blasting housing 1. 
The drum 2 is provided with side walls 10 which are connected with one 
another by means of bars 11 at both ends of the drum with the side walls 
forming the receiving chambers 5 together with dividing walls 12 and 13 
arranged to extend approximately radially of the drum 2. The dividing 
walls 12 and 13 are arranged at a distance from one another between the 
receiving chambers 5 and they are configured to form blasting medium flow 
off channels 14 which are open at both ends. 
The dividing walls 12 extend from the outer circumference of the drum to 
the central area of the drum 2 at a lateral distance from the drum center 
where they form openings 15 in that they reciprocally overlap. The 
dividing walls 13 extend to include an outer dividing wall part 13a which 
is parallel to the dividing wall 12 and which has an angled or bent inner 
dividing wall part 13b extending past the bars 11 and running into or 
toward the next consecutive dividing wall 12 wherein this part forms an 
opening 16 there with the next consecutive dividing wall 12. 
Accordingly, the dividing walls 12 and 13 are arranged in the central area 
of the drum so as to reciprocally overlap wherein the openings 15 and 16 
produce a labyrinthine connection of all of the receiving chambers 5 and 
blasting medium flow off channels 14. 
At the blasting housing 1 there are arranged sealing elements 17, 18, 19 
which are preferably constructed as sealing strips which will ensure 
sealing of the blasting stations 8, 8a relative to the loading and 
unloading station 7 and to the tumbling station 9 as well as a sealing of 
the latter relative to the loading and unloading station. 
Labyrinth seals 20 are also arranged between the rotating side walls 10 and 
the blasting housing 1 thereby creating together with the other seals and 
the dividing walls in the area of the blasting station sealed blasting 
chambers. 
Each of the receiving chambers 5 has located therein a holding device 21 
for holding and supporting in the receiving chambers 5 the workpieces 6. 
The holding devices 21 are provided with a workpiece support 22 and with 
at least one and preferably two clamping or tensioning devices 23. 
The workpiece support 22 is fastened on both sides at a bearing part 24 
with the bearing parts 24 being supported so as to be rotatable about a 
rotational axis 26 in bearings 25 arranged in each of the two side walls 
10. 
Each of the holding devices 21 is driven by means of a geared motor 27 
which is fastened at each side wall 10 and through a chain or belt drive 
28 so that workpieces supported in the holding devices 21 can be rotated 
individually at each process station. Power for the geared motors 27 
rotating with the drum 2 is transmitted preferably through slip rings. 
Each of the clamping devices 23 has at least one clamping claw or shoe 30 
arranged at a swivel lever 29, with the swivel lever 29 being pivotally 
supported at a bearing part 24 and being urged into engagement with the 
workpiece by means of an urging device such as a spring 31. The swivel 
lever 29 includes a second lever arm 32 at which an actuating device 34 
engages in the loading and unloading station 7 in a direction indicated by 
the arrow 33 in order to raise the clamping claw from the workpiece 6. The 
actuating device for urging the swivel lever 29 may be a ram which is 
electromechanically actuated or hydraulically or pneumatically actuated. 
The workpiece support 22 is configured in the form of a grate or grill 45 
and is fastened at the two bearing parts 24 so as to be readily 
exchangeable and/or vertically adjustable whereby as a result of this 
adjustability the distance 36 from a support plane 35 to the rotational 
axis 26 may be adjusted. For flat workpieces in particular, it is 
necessary to raise the grating so that these flat workpieces can be 
clamped to some extent so as to be centered relative to the rotational 
axis 26 for the purpose of uniform blasting procedures. 
The loading and unloading station includes an opening 38 which is adapted 
to be closed by means of a door 37 adapted to be raised and lowered, with 
the opening 38 being adapted to have workpieces 6 loaded or removed 
therethrough, respectively, by means of a loading device 39. 
For this purpose, the holding device 21 is positioned at a particular 
location and the workpieces 6 are fed thereto in a direction indicated by 
the arrow 44. 
The lower part of the blasting housing 1 has an opening 40 beneath which 
there is arranged a vibrator conveyor 41 for carrying away blasting medium 
and blasted particles. 
Centrifugal blasting units 42 are fastened at the circumferential walls of 
the blasting housing 1 and two or more of these units 42 are preferably 
arranged at each blasting process station 8 and 8a, respectively. 
The blasting housing 1 is fastened at a frame 43 upon which the axis or 
axle 3 of the drum 2 is also rotatably supported and at which the geared 
motor 4 is fastened. 
In the operation of the multiple station blasting process machine in 
accordance with the invention described in the foregoing, one or more of 
the workpieces 6 are loaded in a receiving chamber 5 through the opening 8 
at the loading and unloading station 7 by means of the loading device 35. 
The workpieces are securely held in the receiving chambers 5 by the 
holding devices 21 through operation of the spring force provided by the 
spring 31 and as a result they are maintained supported on the grating 45 
by means of the clamping claws 30. 
The drum 2 is then rotated through an angle of 90.degree. thereby allowing 
the workpieces in the receiving chamber which have been loaded at the 
station 7 to reach the first blasting process station 8. At this time, the 
workpieces are set in rotation by turning the geared motor 27 in order 
that they may thereby be processed on all sides by means of the 
centrifugal blasting of the centrifugal wheel units 42. At the same time, 
the second receiving chamber 5 is brought into position at the station 7 
and is loaded with workpieces 6. 
After the drum 2 has been again rotated through an angle of 90.degree., the 
workpieces 6 first loaded into a receiving chamber 5 will enter the second 
blasting process station 8a and a third receiving chamber 5 may then be 
loaded with workpieces 6 at the station 7. When the blasting process is 
terminated, the drum is again rotated by 90.degree. and the finished 
blasted workpieces arrive at the tumble station 9. Here they are again set 
in rotation in order to empty blasting medium from the workpiece cavities 
by means of tumbling operation. 
With the drum 2 being again rotated, the cleaned workpieces will enter the 
loading and unloading station 7 once again where they are brought into the 
removal position by turning the holding device by means of a position 
control at the geared motor 27. 
The empty loading device 39 is moved under the workpiece or workpieces and 
the clamping claws are released by means of rotation of the actuating 
device 34 whereby a workpiece arrives on the loading device 39 and is 
removed from the receiving chamber 5 by this loading devide 39. 
During tumbling or loading and unloading in the stations 9 and 7, 
respectively, the other workpieces can be blast processed in stations 8, 
8a and this is made possible by the reciprocal sealing by means of the 
dividing walls 12 and 13 and by the sealing effected by the seal means 17, 
18, and 19. 
As a result of the arrangement of the dividing walls 12 and 13 which form 
the channels 14 which are open at the outer circumference of the drum, and 
due to their labyrinthine connection with the receiving chambers 5 in the 
center portion of the drum 2, a flow off of the blasting medium and of the 
particles blasted from the blasting stations 8 and 8a is ensured. Also, 
during the blasting process flow off of blasting medium is likewise 
ensured so that there will be no accumulations of the material causing 
disturbances during operation of the machine. The material may be carried 
away in such a manner that it has no disturbing influence on the tumbling 
process or on the loading and unloading process. 
By assigning a rotation drive for the workpieces in each station, different 
numbers of revolutions, rotational directions and stopping periods of the 
workpieces in the individual stations are made possible and it is also 
possible to retain a determined holding position in the loading and 
unloading station. 
The arrangement of four receiving chambers with up to four workpieces each, 
one behind the other, results in a compact machine displaying high 
efficiency wherein the workpieces can also be blast processed at both end 
faces simultaneously. 
The individual rotational drives for the workpieces, which rotational 
drives are protected from the blasting medium, makes it possible in each 
blasting process station and in the tumble station to apply different 
rotational movement for the workpieces which may be adapted to the form of 
the workpieces in order to achieve a uniform blast processing. 
The multiple station blasting process machine in accordance with the 
invention is especially suitable for workpieces which are not adapted for 
treatment in drums such as, for example, engine blocks, cylinder means 
gear unit housings and the like. 
Thus, it will be seen that the present invention provides a multiple 
station blasting process machine which is essentially comprised of a 
conveyor means constructed as a cylindrical drum 2 wherein workpieces 6 
are held by means of holding devices 21 in a plurality of receiving 
chambers 5. The respective workpieces 6 lying in a receiving chamber 5 
will be conveyed through two blasting process stations 8, 8a and through a 
tumble station 9 and then back to a loading and unloading station 7 by 
means of stepwise rotation of the conveyor drum 2. The receiving chambers 
5 which are uniformly distributed about the circumference of the drum are 
enclosed by walls 10, 12 and 13 which are fastened at the drum 2 and in 
such a manner that together with the surrounding blasting housing 1 they 
form a sealed blasting chamber in the area of the blasting process 
stations 8, 8a. Flow off of the blasting medium and of particles blasted 
from the workpieces is ensured at all times by the arrangement of the 
blasting medium flow channels 14 which enable effective outflow of the 
blasting medium as a result of their labyrinthine connection at the center 
portion of the receiving chamber 5 with the channels 14 being open at the 
outer circumference of the drum. 
While a specific embodiment of the invention has been shown and described 
in detail to illustrate the application of the inventive principles, it 
will be understood that the invention may be embodied otherwise without 
departing from such principles.