GB991783A - Improvements in and relating to nuts and bolts - Google Patents

Abstract

991,783. Bolt-tensioning; locking nuts. P. & O. PILGRIM VALVE Ltd. Sept. 13, 1961 [Oct. 7, 1960], No. 34521/60. Heading F2H. [Also in Division G1] In order to tension a bolt 1 or stud, fluid under pressure, such as grease from a gun, is introduced into a passage 8 in a rubber body 7 to force an annular piston 6 (26) out of a cavity 5 (25) formed in a nut 4, Fig. 1, or in a ring 24, Fig. 6, set beneath a nut, or in a bolthead 3, Fig. 5. The nut 4 or bolt-head 3 is first tightened by hand or tommy bar against a split ring 14 which is of such a thickness that the unstressed rubber body 7 fills its space in the cavity 5 and then, when the tension has been applied to the bolt 1, the split ring is removed and replaced by a thicker one which is gripped when the pressure of the fluid in the body 7 is released. Incidentally, locking of the nut 4 is achieved by the urging of the part of the nut thread adjacent the body 7 into the bolt thread by the fluid pressure. The rubber body 7 may be flattened, Fig. 2 (not shown), to fill its space in the cavity 5 before tensioning, and may be formed by cementing a flat ring at two spaced annular zones on a second ring, Fig. 3 (not shown), in which case the two rings may each have a groove, the grooves combining to form the passage 8. The body 7 may be of a circular cross-section, Fig. 5, and located in a cavity in a ring, Fig. 4 (not shown), set beneath the nut 4 as is the ring 24 shown in Fig. 6. The rubber body 7 in Fig. 6 may be bonded to the piston 26. It envelops a thin soft metal tube 27 soldered in the recess 25. Pressure fluid is introduced into the tube until it bursts the tube and deforms the rubber body 7 to tension the bolt 1. The elongation of the bolt may be gauged by a rod 31 which is secured at one end in an axial bore in the bolt so that it is not subject to the applied tension. When the required elongation is achieved, the thickness required for the second split ring to maintain the desired tension is calculated by measuring the gap beneath the nut or bolt head and rings of such thickness may then be used with similar accompanying bolts without further gauge rods 31 being required to indicate that tension. As shown in Fig. 7, a device for indicating when the bolt 1 has been sufficiently elongated may include a lamp 36 which is on when the device is tilted as indicated but goes out when the bolt end rises and moves a micrometer spindle 35 out of contact with the gauge rod 31. The spindle 35 is first set to protrude the required elongation distance from the end of a central hole in an annular magnet 33 (which is mounted on insulation 34 on the end of the micrometer) for holding the device on the bolt end. Specification 980,090 is referred to.