Heliovaara and Patten had already seen off two British pairs to reach the last four, first beating Dan Evans and Henry Searle in straight sets, then needing a 10-point tiebreak to beat David Stevenson and Marcus Willis.
The first set saw neither pair break serve, though the Finn and Brit were forced to save set point and level the scores at 6-6. In the tiebreak, however, despite forcing a loss of serve with the first point, Heliovaara and Patten had their serve broken three times, losing 7-3 for a 7-6 first-set defeat.
In yesterday's Quarter-final, the second seeds rallied after losing the first set, but their looked to be little chance of a repeat when they lost serve in the opening game of the second set.
Yet, the two-time grand slam champions found their rhythm, breaking back to level the scores at 3-3, before making it two-in-a-row against Cash and Glasspool's serve to take a 5-3 lead, before wrapping up a 6-3 set victory.
However, an early loss of serve in the 10-point tiebreak handed the initiative back to the all-British side, and the Heliovaara and Patten could not find a route back.
They managed to save the first match point to make the score 9-6, but they could not prevent the fourth seeds from getting the job done at the second time of asking, securing a 7-6, 3-6, 10-6 win.
Cash and Glasspool move onto the Final at the London grass court event, where they will meet Croatia's Nikola Mektic and New Zealand's Michael Venus.
