| # | Country | Total Patents | |
|---|---|---|---|
| #1 | United States | 2 | |
| #2 | Belgium | 1 | |
| #3 | Canada | 1 | |
| #4 | Germany | 1 | |
| #5 | France | 1 | |
| #6 | Japan | 1 | |
| #7 | Mexico | 1 | |
| #8 | Netherlands | 1 | |
| #9 | Norway | 1 | |
| #10 | Portugal | 1 |
| # | Industry | |
|---|---|---|
| #1 | Civil engineering |
| # | Technology | |
|---|---|---|
| #1 | Foundations and excavations | |
| #2 | Sewers |
| # | Name | Total Patents |
|---|---|---|
| #1 | Helms William R | 4 |
| #2 | Helms Williams R | 1 |
| #3 | Helms William Richard | 1 |
| #4 | Uiriamu Aaru Herumusu | 1 |
| Publication | Filing date | Title |
|---|---|---|
| US4145151A | Manhole cover and frame work | |
| CA1089275A | Method and apparatus for elevating load-bearing access devices |