Since its dicult to hold the sample in place without damaging/contaminating it and assuring that it would stay when in vertical position, it was designed a platform that "sucks" the sample against its surface, holding it in its place.
Figure 47: Trimetric view of the 3 platforms that constitute as vacuum platform
This vacuum platform is composed of 3 adjacent platforms connected by a screw from the top to the threads on the bottom one, each one with its unique purpose.
The bottom one has the purpose of positioning the other two platforms, with the horizontal rotating axis in the middle.
The middle platform has 4 dierent grooves for o-rings, and 4 other grooves for the vacuum circuit.
(a) Top view of the middle component with the o-ring gooves highlighted in green and the vacuum paths highlithed in blue.
(b) Side view of the middel and top components where is possible to see the vacuum pathway.
Figure 48: Two views of the same component, by comparing both images above is possible to comprehend the vacuum path and how it is applied to the sample uniformly
As is possible to see in the gure 48, there are 4 vacuum channels highlighted in blue connected to a vacuum machine, each one separated by o-rings highlighted in green. Each o-ring determines the active area of the vacuum created in that isolated volume. Meaning that if the sample being studied has a diameter of 15mm, there is only a need for one vacuum circuit to be on, which would be the second one counting from the left(Figure 50 (b)). The bigger the sample is more active vacuum circuits we need to have on at the same time, so assure that the sample is steadily secure to the platform. Having these dierent vacuum paths allows the usage of samples from 15mm to 50mm, although there is not a maximum sample size since it can be bigger than the platform or have an irregular shape.
(a) Top view of the middle component (b) Top view of the middle component with transparent top component
Figure 49: Two views of the same component, where is possible to see that the set of hole coincide with a second set of grooves done on the middle component
(a) Trimetric view of the top
component (b) Trimetric view of the middle component with the o-ring grooves
highlighted
Figure 50: Top and middle platforms, (a) Top component with the vacuum holes that coincide with the vacuum groove, (b) Middle platform with both vacuum and o-ring grooves
The top component is composed of a slab of metallic material with tinny holes so the negative pressure can reach the sample. When the 3 platforms are assembled and screw together tightly, those tinny holes will coincide with the vacuum grooves, this allows the vacuum to reach every hole more easily.
In case of an irregular-shaped sample has to be measured, the remaining holes of the corresponded vacuum size that is in use, have to be sealed. This can be achieved by placing a small rubber plug on the remaining holes.
6.6.2 Sample positioning platform
To make sure the sample is placed safely and correctly on the vacuum platform it would be better to place it while the platform is in the horizontal position. Once the sample is placed and the vacuum is turned on, the platform needs to be rotated to the vertical position so the sample can be pressed against
the o-ring of the ECV box. At rst, was thought to construct a joint that could lock on both vertical and horizontal positions.
(a) Side view of the sample positioning platform
with the sample positioned verticaly (b) Side view of the sample positioning platform with the sample positioned horizontaly
Figure 51: Side view of the positioning platform rst design, (a) on the vertical position the sample is ready to be squeezed against the ECV o-ring, (b) on the horizontal position is possible to place the sample and select the area which will be analysed
Since the stopping ap would have to be welded on, if done wrong, the platform could never get to the vertical position perfectly which results in leaking electrolyte.
So the second design was to have a rotating horizontal axis in the middle with only one apper to stop it horizontally, so for the vertical position, the platform can correct itself by applying pressure against the sample o-ring, since the rotating axis is at the same height as the sample o-ring center, assuring that there is not going to happen any leakage.
(a) Side view of the sample positioning platform
with the sample positioned horizontaly (b) Side view of the sample positioning platform with the sample positioned verticaly
Figure 52: Side view of the positioning platform nal design, (a) on the vertical position the sample is ready to be squeezed against the ECV o-ring, (b) on the horizontal position is possible to place the sample and select the area which will be analysed
Later was added a magnet both to the platform and on the apper so it could stop the platform from rotating if any tension from the vacuum tubes acted.
Figure 53: Close view of the Thrust ball bearing system
As we can see from the gure 53, the axis of the thrust ball bearing is screwed into the platform, meaning that it self will rotate when alternating between horizontal and vertical positions. This rotation becomes troublesome because of the need for the thrust ball bearing to be tight between both surfaces, so since alternating positions would unscrew the bolt, it was added a second thrust ball bearing to rotate with the bolt and the screw, maintaining it tight. A second nut can be added if it continues to unscrew with usage.
Figure 54: Top view of the Sample positioning platform