axes a and b via support pins 544 546 a speed changing link 548 is pivotally connected to the second link 536 about a support pin 549 the speed changing link 548 selectively pivots into and out from engagement with the first gripper plate 528 by way of a switch 550 the speed changing link 548 pivots between a high speed position and a low speed position about the support pin 549 the low speed position is shown in fig2 the high speed position corresponds to faster advancement of the drive rod 524 at a lower force this allows the user to quickly advance the drive rod 524 to drive the piston 114 and dispense high volumes of bone cement at low pressure the low speed position corresponds to slower advancement of the drive rod 524 at a higher force which exerts more force on the piston 114 to pressurize the bone cement the first gripper plate 528 and the speed changing link 548 have complementary first and second coupling devices 552 554 used to couple the first gripper plate 528 with the speed changing link 548 in the high speed position more specifically in the embodiment of fig2 the first.