This invention relates to an pneumatically powered installation tool for installing fasteners such as lockbolts, i.e. fasteners comprising a groove stem including a breaker groove, and a collar.

Known tools for installing lockbolt fasteners install the lockbolt into a workpiece by swaging the collar onto the grooved stem. On depression of the tool trigger, a pull stroke is initiated, whereby compressed air is fed to one side of a double-acting pneumatic piston, thereby causing movement of the piston and of an intensifier rod which is coupled to the piston. The movement of the piston and rod causes movement of a head piston, which in turn causes actuation of the jaws within the tool head. The tool applies a pulling force to the stem of a fastener via the jaws, thereby causing a collar to be swaged onto the stem. The pulling force is applied until the stem is caused to break at the breaker groove. The tool applies a 'push-off force via reversed movement of the head piston, to eject the collar from the tool head.

After the trigger is released, a return stroke is initiated whereby the head piston and the pneumatic piston return to their original positions.

In currently known lockbolt installation tools, two hydraulic lines are provided to the head to produce the double-acting piston motion which is required to install the lockbolt. These hydraulic lines are usually provided by the double-acting pneumatic piston which actuates the intensifier rod which acts in both directions of movement.

However, in prior art tools in which the two hydraulic lines are of fixed volumes, any oil loss in the pull side causes a loss of stroke and a vacuum condition during the return stroke, causing aeration of the oil and reduced tool performance. Any oil loss in the return side prevents the head piston from fully returning, which in turn results in reduced engagement of the tool jaws on the lockbolt stem, thereby increasing the chance of failure of the tool nose equipment or the lockbolt.

To counter the above effect, an oil reservoir and a pressure relief valve is normally used to provide a secondary circuit, providing additional hydraulic volume. Oil from the reservoir is drawn in when there is an imbalance in the oil volumes, and when the head returns to its end stop, any excess volume is pushed through the pressure relief valve.

The provision of the oil reservoir and pressure relief valve increases tool complexity, bulk, and cost. Furthermore, if the pressure relief output valve is connected to the pull side, and there is an obstruction preventing the head from fully returning, excess oil is discharged into the pull side. This results in the head piston starting the cycle partially back, thereby again reducing engagement of the tool jaws with the grooved stem of the lockbolt, and increasing the chance of failure of the tool nose equipment or the lockbolt. An aim of the current invention is to provide a lockbolt installation tool which does not suffer from a gradual loss of stroke, which ensures full engagement of the tool jaws with the grooved lockbolt stem and thereby prevents potential failure of the tool nose equipment or the lockbolt.

Accordingly the present invention comprises a tool as claimed in claim 1 of the appended claims. The present invention uses floating pistons to provide compliance when transmitting pressure from the double acting pneumatic piston to the head piston. In the volume between the floating pistons, air is provided via a vent to atmosphere. The floating pistons are free to take whatever position dependent upon the hydraulic displacement. Any oil loss on the pull stroke will not cause a vacuum condition in the oil volumes within the tool.

A first embodiment of the present invention includes a secondary oil circuit, comprising a positively pressured oil reservoir connected via a check valve and a pressure relief valve (in parallel) to the return side of the main channel.

In a second embodiment aspect of the present invention, a secondary reservoir is not provided. Instead, an integrated reservoir is provided by an excess of oil in the return volume itself. Therefore, there is a lost pneumatic piston stroke in a normal cycle. However, if oil is lost from the return side, extra pneumatic piston stroke is available. As oil is lost, the hydraulic pull and return pistons move apart from each other within the main channel. Preferably a seal is provided, which is fitted to the pneumatic piston, and acts to seal the air inlet / exhaust on the pull side when the pneumatic piston is at the end of the return stroke.

Preferably a small diameter aperture through the pneumatic piston is also provided. The aperture acts as an air bleed across the piston, i.e. between the pull and return sides of the pneumatic piston, thereby equalising the pressures on either side when the tool is at rest. As there is a larger area on the return side of the pneumatic piston, pressure is always maintained on the seal to ensure sealing. However, the pressure on the return side of the head piston is greatly reduced.

The seal and the small diameter aperture act to reduce the hydraulic pressure which is held on the return side of the head piston during tool inactivity.

Because the reservoir in the second embodiment is integrated, the component count of the tool is reduced, and tool complexity, bulk and cost are reduced. Embodiments of the invention will now be described by way of example only and with reference to the figures in which;

Figure 1 is a cross-sectional view of tool in accordance with a first embodiment the present invention, wherein the tool is in an initial position;

Figure 2 is cross-sectional view of the tool of Figure 2 wherein the tool is at the end of the pull stroke; Figure 3 is a cross-sectional view of the tool of Figure 1 wherein the tool is at the start of the return/push-off stroke;

Figure 4 is a cross-sectional view of the tool of Figure 1 wherein the tool is at the end of the return/push-off stroke and start of the reservoir exchange;

Figure 5 is a side view of a tool in accordance with a second embodiment the present invention; Figure 6 is an underside view of the tool of Figure 5;

Figures 7a to 7d are isometric views the tool of Figure 5;

Figure 8 is a rear view of the tool of Figure 5; Figure 9 is a front view of the tool of Figure 5;

Figure 10 is a cross-sectional view of the second embodiment of the tool along the lines D-D of Figure 8 when the tool is in a rest position;

Figure 1 1 is a cross-sectional view of the second embodiment of the tool along the lines E-E of Figure 8 when the tool is in a rest position;

Figure 12 is a cross-sectional view of the second embodiment of the tool along the lines F-F of Figure 8 when the tool is in a rest position;

Figure 13 is a cross-sectional view of the second embodiment of the tool along the lines A-A of Figure 9 when the tool is in a rest position; Figure 14 is a cross-sectional view of the second embodiment of the tool along the lines B-B of Figure 9 when the tool is in a rest position;

Figure 15 is a cross-sectional view of the second embodiment of the tool along the lines C-C of Figure 9 when the tool is in a rest position;

Figure 16 is a cross-sectional view of the second embodiment of the tool along the lines D-D of Figure 8 when the tool is at the end of the pull stroke; Figure 17 is a cross-sectional view of the second embodiment of the tool along the lines E-E of Figure 8 when the tool is at the end of the pull stroke; Figure 18 is a cross-sectional view of the second embodiment of the tool along the lines F-F of Figure 8 when the tool is at the end of the pull stroke;

Figure 19 is a cross-sectional view of the second embodiment of the tool along the lines A-A of Figure 9 when the tool is at the end of the pull stroke;

Figure 20 is a cross-sectional view of the second embodiment of the tool along the lines B-B of Figure 9 when the tool is at the end of the pull stroke;

Figure 21 is a cross-sectional view of the second embodiment of the tool along the lines C-C of Figure 9 when the tool is at the end of the pull stroke;

Figure 22 is a cross-sectional view of the second embodiment of the tool along the lines D-D of Figure 8 when the tool is at the start of the return/push-off stroke; Figure 23 is a cross-sectional view of the second embodiment of the tool along the lines E-E of Figure 8 when the tool is at the start of the return/push-off stroke; Figure 24 is a cross-sectional view of the second embodiment of the tool along the lines F-F of Figure 8 when the tool is at the start of the return/push-off stroke;

Figure 25 is a cross-sectional view of the second embodiment of the tool along the lines A-A of Figure 9 when the tool is at the start of the return/push-off stroke;

Figure 26 is a cross-sectional view of the second embodiment of the tool along the lines B-B of Figure 9 when the tool is at the start of the return/push-off stroke

Figure 27 is a cross-sectional view of the second embodiment of the tool along the lines C-C of Figure 9 when the tool is at the start of the return/push-off stroke;

Figure 28 is a cross-sectional view of the second embodiment of the tool along the lines D-D of Figure 8 when the tool is at the end of the return/push-off stroke, with a full oil reservoir; Figure 29 is a cross-sectional view of the second embodiment of the tool along the lines E-E of Figure 8 when the tool is at the end of the return/push-off stroke, with a full oil reservoir; Figure 30 is a cross-sectional view of the second embodiment of the tool along the lines F-F of Figure 8 when the tool is at the end of the return/push-off stroke, with a full oil reservoir;

Figure 31 is a cross-sectional view of the second embodiment of the tool along the lines A-A of Figure 9 when the tool is at the end of the return/push-off stroke, with a full oil reservoir;

Figure 32 is a cross-sectional view of the second embodiment of the tool along the lines B-B of Figure 9 when the tool is at the end of the return/push-off stroke, with a full oil reservoir;

Figure 33 is a cross-sectional view of the second embodiment of the tool along the lines C-C of Figure 9 when the tool is at the end of the return/push-off stroke, with a full oil reservoir;

Figure 34 is a cross-sectional view of the second embodiment of the tool along the lines C-C of Figure 9 when the tool is at the end of the return/push-off stroke, with an empty oil reservoir Figure 35 is a cross-sectional view of the second embodiment of the tool along the lines C-C of Figure 9 when the tool is at the end of the return/push-off stroke, with an empty oil reservoir;

Figure 36 is a cross-sectional view of the second embodiment of the tool along the lines C-C of Figure 9 when the tool is at the end of the return/push-off stroke, with an empty oil reservoir.

Referring to Figures 1 to 4, a tool 2 according to a first embodiment of the present invention comprises a head section 4 comprising a head piston 6, a handle section 10, a base section 12 and a trigger 14. The tool further comprises pneumatic installation means, comprising a pneumatic piston 16 within the base section 12 coupled to an intensifier rod 18 with a T-section 20 provided at the end of the rod 18 remote from the pneumatic piston 16. The rod 18 extends into a main channel 22 within the handle section 10 of the tool 2. A pull piston 24 and a return piston 26 are provided within the main channel 22. The pull piston 24 and the return piston 26 are not affixed to the rod 18 or the walls of the channel 22, and are therefore free to 'float' axially within the main channel 22, i.e. they are free to move within the main channel 22 in an axial direction with respect to the main channel 22.

The main channel 22 is divided into three sections by the pull piston 24 and the return piston 26: a return side 22a, between the return piston 26 and the tool head section 4, a mid portion 22b, between the return piston 26 and the pull piston 24, and a pull side 22c, between the pull piston 24 and the base section 12 of the tool. The volume of each of the three sections is dependent upon the relative positions of the pull piston 24 and the return piston 26, and therefore varies throughout the tool cycle. An air vent channel 28 is provided in the handle section 10 of the tool

2 leading into the main channel 22, thereby providing a vent to atmosphere from the main channel 22.

A secondary oil circuit 30 is provided within the handle section 10 of the tool 2. The secondary oil circuit 30 comprises a positively pressured oil reservoir 32 which is connected via a check valve 34 and pressure relief valve 36 in parallel to the check valve 34. The check valve 34 is checked in the direction from the return side 22a into the reservoir 32. A floating reservoir piston 40 is provided within the reservoir 32.

In the initial position of the tool 2, as shown in Figure 1 , the pneumatic piston 16 is at the top (i.e. closest to the head section) of the base section 12 of the tool 2. Operation of the tool 2 is effected by depression of the tool trigger 14, thereby causing initiation of a pull stroke. During the pull stroke, compressed air is fed into the tool by a hose (not shown) via an air supply channel 38, and causes the pneumatic piston 16 and rod 18 to move away from the tool head section 4. The head piston 6 is therefore caused to retract, and the jaws (not shown) are thereby actuated to apply the necessary pulling force to the stem of a lockbolt (not shown) to swage the collar of the lockbolt onto the stem and subsequently to break the stem at a breaker groove, thereby installing the lockbolt.

During the pull stroke, as the rod 18 moves through the main channel 22 away from the tool head section 4, the T-section 20 contacts the pull piston 24 and causes the pull piston 24 also to move along the main channel 22 away from the tool head section 4. The return piston 26 is free to float within the main channel 22 between the T-section 20 and the tool head section 4. The air vent channel 28 allows the pressure on the return side 22a and in the mid portion 22b to be equalised.

During the pull stroke of the tool, when there is minimal pressure in the return side 22a of the main channel 22, the positive pressure of the secondary oil circuit 30 causes oil to be pushed from the reservoir 32 into the return side 22a via the check valve 34 as shown in Figure 2.

Release of the trigger 14 causes initiation of a return/push-off stroke, wherein the pneumatic piston 16 and rod 18 return to the initial position of Figure 1 . As the rod 18 moves along the main channel 22 towards the tool head section 4, the T-section 20 contacts the return piston 26 and pushes it towards the tool head section 4 as shown in Figure 3. On the return stroke, the pull piston 24 is free to float within the main channel 22, thereby ensuring a vacuum condition does not occur on the pull side 22c. The air vent channel 28 allows the pressure on the pull side 22c and in the mid portion 22b to be equalised. During the return stroke of the tool 2, the check valve 34 prevents oil from being pushed into the reservoir 32 from the return side 22a of the main channel 22. When the head piston 6 is at the end stop, as shown in Figure 4, the pressure relief valve 36 cracks open, thereby allowing excess oil to be pushed back into the reservoir 32. Figure 1 shows the tool 2 after the exchange of oil into the reservoir 32 has been completed.

In the embodiment shown in Figures 1 to 4, the secondary oil circuit 30 is provided within the handle section 10. However, the secondary oil circuit 30 could be located elsewhere on the tool, for example in the head section 4.

A second embodiment of the present invention, as illustrated in Figures 5 to 33, differs from the first embodiment in that a secondary oil circuit 30 is not provided. Instead, the tool 2' comprises an integrated oil reservoir, which is provided by an excess volume of oil on the return side 22a, i.e. more oil is provided on the return side 22a than with the first embodiment. This leads to a loss of pneumatic stroke during a normal cycle of the tool 2'. However, if oil is lost from the return side 22a of the main channel 22, extra stroke (shown at 44 on Figures and 14 and 31 ) of the pneumatic piston 16 is available.

The tool 2' of the second embodiment comprises a seal 46 and a small diameter aperture 17a preferably formed in screw 17, both provided on the pneumatic piston 16, which in combination act to reduce the hydraulic pressure which is held on the return side of the head piston 6 during tool inactivity. The seal 46 acts to seal the air inlet / exhaust on the pull side when the pneumatic piston 16 is at the end of the return stroke as shown in Figure 28.

The small diameter aperture is provided through the pneumatic piston 16, and acts as an air bleed between the pull side 16a and return side 16b of the pneumatic piston 16, thereby equalising the pressures on either side of the pneumatic piston 16 when the tool 2' is at rest. As there is a larger area on the return side 16a of the pneumatic piston 16, pressure is always maintained on the seal 46 to ensure sealing. However, the pressure on the return side of the piston is greatly reduced by the air bleed.

In the second embodiment of the present invention, the lack of secondary oil reservoir reduces tool cost, bulk and complexity.