Pneumatic collar installation tool

Abstract: A pneumatic collar installation tool has a plunger assembly (16) which advances from a retracted position near the rear of the tool through a collar pickup station to an extended position extending from the front of the tool. A collar shuttle (14) delivers a collar or nut in front of the plunger assembly (16) before it reaches the collar pickup station and retracts away from the collar pickup station before the plunger assembly moves through that station. The collar is picked up on an assembly (17) that includes a split spring ring (33) which engages the bore of the collar. The spring ring is mounted on a fixed member, which also includes a hexagonal key (27) for preventing rotation of a bolt as the collar is threaded onto it. A rotating collar driver (36) moves over the outside of the collar picked up by the collar pickup assembly for threading the collar onto a bolt.

Description: This invention relates to a tool for installing threaded collars on a threaded pin or the like. It is particularly useful for installing a collar as described in U.S.-A-4,260,005 although also useful for standard hexagonal nuts or the like. Parts of the total tool described may be used for installing unthreaded collars. Background of the Invention A variety of automatic tools have been developed over the years for rapidly installing nuts or collars on high-strength aerospace fasteners. The terms nut and collar are used interchangeably. Typically these automatic tools are pneumatically operated and can be used rapidly so that the myriad number of fasteners on modern aircraft or the like can be installed with a minimum amount of assembly time. There are a variety of requirements for such tools. Collars should be automatically delivered to the tool in a position to be quickly installed on a bolt without manual intervention by the operator. For example, the tools should be useable in any orientation since the fasteners to be assembled may sometimes be overhead or beneath the worker or in front of the worker using the tool. For threaded fasteners, it is often desirable to provide a nonrotating key coaxial with a rotating nut to keep the threaded fastener or "pin" from rotating until the nut is installed. Naturally, there are certain operating efficiencies which are also desirable. For example, the tools should operate quickly and reliably to provide uniform tightening of nuts on bolts. Preferably the time between installing one nut and having the next nut ready for installation should be minimized. The amount of air usage should be minimized. Some collars, such as those in US-A-4,260,005, have a flange which is assembled against the workpiece being connected by the fastener. The mechanisms for handling such collars must be designed to accommodate such a flange. The flange geometries may vary with different embodiments of collars and some adaptability in that regard is therefore desirable in the automatic collar installation tool. The present invention commences from EP-A-0,368,813 which discloses a tool according to the opening part of claim 1 appended hereto. According to this invention, therefore, there is provided a collar installation tool comprising a shaft, means for retaining a collar on the shaft and means around the shaft for fastening a collar on a pin or bolt, characterized by the retaining means comprising : a circumferential groove in the shaft; and a spring ring on the shaft having a larger inside diameter than the bottom of the groove in the shaft for freely rotating on the shaft, a larger outside diameter than the inside diameter of a collar, and a longitudinally extending split for accommodating changes in diameter for receiving a collar around the outside diameter of the ring and resiliently holding the collar. The tool has a non-rotatable shaft within the rotatable member. A split spring ring on the shaft picks up the collar at the collar-delivery station and resiliently holds it. The spring ring rotates when the collar rotates during assembly on a bolt. The non-rotatable shaft includes a key for keeping a bolt from rotating. There are also means for resiliently biasing the shaft within the rotatable driver for accommodating axial advance of the driver along the length of the collar. When the installation tool operates, a collar-delivery plunger axially shifts from a retracted position to a pick-up position where the split ring on the shaft enters the bore of a collar in the shuttle. The collar shuttle is then retracted for clearing the collar as it advances further with the plunger. The plunger then advances a second distance toward a workpiece where it is threaded onto a bolt by the rotating driver. Meanwhile, another collar is fed to the collar shuttle in its retracted position. The present invention will now be described by way of example in the following detailed description when considered in connection with the accompanying drawing wherein: FIG. 1 is a detail, in partial longitudinal cross-section, of the collar pickup assembly. A collar pickup mechanism includes a hexagonal key 27 which passes through the hexagonal hole of a retaining ring 28 threaded into the end of a plunger tube 19 with a left-hand thread to keep it from coming loose during use of the tool. The end of the key engages a movable plug 29 which can slide axially within the tube. The retaining ring 28 keeps the plug 29 within the tube. The plug is biased toward the front of the tube by a long coil spring (not shown). A stepped shaft 32, which also has a hexagonal hole, fits on the other end of the key 27. A collar retaining spring ring 33 fits in a circumferential groove around the stepped shaft 32. In use, the key 27 serves to engage a correspondingly-shaped recess in a threaded pin onto which a collar is to be threaded, to prevent the pin from rotating with the collar. The spring ring is generally barrel-shaped to provide an external lead for entering the bore of a collar. The outside diameter of the spring ring is slightly larger than the diameter at the crest of the thread in the collar. Thus, as the spring ring moves into the collar, the ring is compressed and frictionally engages the bore of the collar along the thread crest. The degree of compression of the spring ring by the collar and clearance between the inside of the spring ring and the groove in the stepped shaft are sufficient that, when fully compressed by a standard collar, there is still clearance between the shaft and ring and the ring can rotate relative to the shaft. To get the appropriate frictional contact between the spring ring and thread in an exemplary embodiment, for gripping a number 10 nut, the ring has an outside diameter of 4.2 millimeters, a wall thickness of 0.18 millimeter, a length of 3 millimeters, a lead of 15 degrees over 1/4 of the length of the spring ring. The ring has a slot about 1/2 millimeter wide on one side at an angle of about 15 degrees from the axis of the ring. A radial clearance of about 0.2 millimeter between the ring and shaft permits free rotation of the ring when inserted in a nut. Other dimensions would be appropriate for other sizes of nuts. As noted above, the plug 29 in the plunger tube is spring biased toward the front end of the tube by the coil spring (not shown), which bears at its opposite end against the plug 24 which is fixed relative to the housing of the tool. The spring is designed so that when the plunger assembly is in its retracted position, the spring force is about 4.5 to 5 kilograms. Thus, as the plunger assembly moves from its retracted position to the collar pickup position, there is a force of about 4.5 to 5 kilograms pressing the ring into the collar, which is adequate for securely mounting the collar on the spring ring. On the other hand, when the plunger assembly is in its fully extended position, the spring force biasing the collar pickup assembly forward drops off to about 1/2 to 1 kilogram. The lower spring force makes it easier to place the collar on the bolt and advance the collar driver over the collar.

Claims: A collar installation tool comprising a shaft (32), means for retaining a collar on the shaft and means around the shaft for fastening a collar on a pin or bolt, characterized by said retaining means comprising: a circumferential groove in the shaft (32); and a spring ring (33) on the shaft having a larger inside diameter than the bottom of the groove in the shaft for freely rotating on the shaft, a larger outside diameter than the inside diameter of a collar, and a longitudinally extending split for accommodating changes in diameter for receiving a collar around the outside diameter of the ring (33) and resiliently holding the collar. A collar installation tool according to claims 1 further comprising a non-rotating key (27) coaxial with the shaft (32) and extending therefrom for engaging a threaded pin or bolt to prevent rotation of the threaded pin or bolt when threading a collar thereon.

Inventors: LOUW JOHN A, LOUW, JOHN A.
Applicants: FAIRCHILD HOLDING CORP, FAIRCHILD HOLDING CORP.
Application year: 1991
Main classification: B25B23
IPC codes: B25B21, B25B23