All about the raised rim, safety lip, or gruve/gard
Many people have asked me why I didn’t include anything about the “raised rim” in my guide to the parts of a lp record. Actually, no one asked me that, but it’s a legitimate question.
The raised rim is the thicker portion at the outer edge of the record. Most people are probably so used to records with a raised rim that they’ve never really thought about why it’s there. So I’ll tell you.
Like the 78s that preceded them, early vinyl LPs and 10″s were the same thickness from the center to the rim. Flat. This was a pretty sensible design but it did have one drawback. It was common for people to use “record changers” at that time. Record changers allowed you to stack up records and automatically play them one after the other. It was convenient, but not good for the records. The grooves of two records on the stack could rub against each other, leading to possible damage to the delicate groove edges.
In 1954, Donald L Richter of RCA patented a design for a record with a thicker center and outer rim. The stated goals were to protect the fragile groove ridges from damage when records were stacked and to protect the record when taking it in or out of the record jacket. There was also a third goal. Since the grooved portion of the record was thinner, that meant less vinyl was used when making each record. According to an article in RCA Engineer (Vol 22, No 3) entitled “Engineering and music at RCA Records”, this new profile “reduced record weight from 185 to 135 grams”.
In September of 1954, RCA started producing records with the new Gruve/Gard profile and offered the technology to other record companies license-free. The 18 September 1954 issue of Billboard noted that Capital had been working on their own similar idea for over a year. Obviously this was an idea whose time had come and it caught on quickly.