| CPC F04B 53/16 (2013.01) [F04B 43/02 (2013.01)] | 22 Claims |

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1. A tightening device comprising:
an assembly configured to apply preload to at least one fastening element of a diaphragm pump head, the at least one fastening element comprising a bearing surface at a head end of the at least one fastening element, wherein the assembly comprises:
a support comprising:
a support surface arranged to engage with the bearing surface at the head end of the at least one fastening element, and
a threaded hole extending from the support surface entirely through the support to an opposite side;
a screw element comprising a contact surface at a front end of the screw element, wherein the screw element penetrates through the threaded hole with the contact surface of the screw element positioned on the opposite side of the support from the support surface of the support; and
a pressure plate positioned between the diaphragm pump head and the support, wherein the contact surface of the screw element contacts the pressure plate,
wherein rotation of the screw element alters a distance between the contact surface of the screw element and the support surface of the support, thereby, altering a preload applied to the bearing surface of the at least one fastening element.
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