WO2001051254A1

WO2001051254A1 - Mechanical safety and trigger mechanism for primarily gas-powered tools

Info

Publication number: WO2001051254A1
Application number: PCT/SE2001/000046
Authority: WO
Inventors: Göran Olofsson; Sten Sundberg
Original assignee: Saab Bofors Dynamics Ab
Priority date: 2000-01-13
Filing date: 2001-01-12
Publication date: 2001-07-19
Also published as: SE517518C2; SE0000080D0; AU2001228955A1; SE0000080L

Abstract

The present invention relates to a mechanical safety and trigger mechanism for tools powered by combustion gases from a propellant-charged power unit (23) of a type initiated by an integral percussion primer that is activated by a piston spring (15) driven firing pin (17). The key feature of the device as claimed in the present invention is the safety concept that is fully integrated into the trigger function which means that to enable the trigger (12) to actuate the catch (27) that holds the firing pin (17) in cocked position with the piston spring (15) compressed, the said trigger is arranged to be displaceable in two principally mutually perpendicular directions (A and B respectively), of which the first motion (A) is necessary to enable the second (B) to actuate the catch (27) in such a direction that the firing pin (17) is released and the tool is initiated.

Description

MECHANICAL SAFETY AND TRIGGER MECHANISM FOR PRIMARILY GAS-POWERED TOOLS

The present invention relates to a mechanical safety and trigger mechanism for gas- powered tools. Gas-powered cutting, impact and hole-punching tools are mainly used under difficult conditions, such as in conjunction with rescue operations or when one is a long way from more convenient energy sources such as electricity. The expression 'difficult conditions' refers to location as well as time of day, weather and the stress factor. Moreover, when there is a major risk of fire or explosion, gas-powered cutters can be more suitable than other spark-forming tools or tools that operate with an open flame such as compressed-air driven or electrically driven abrasive cutting-off wheels or burners.

A common factor for most occasions for when a gas-powered tool is relevant is thus when major requirements are that the tool shall be easy to operate, and that it shall be operable by personnel with limited prior experience of the tool in question. Briefly, it must be possible to operate such tools under all sorts of conditions and weather, and it must not be possible to trigger their active function in such a way that could cause an accident.

To meet the requirements stated above we have now produced the safety and ignition device described below for gas-powered tools.

The present invention will be described in conjunction with a gas-powered cutter, which is the most common type of gas-powered tool, but this shall not be regarded as limiting in any way the more general applicability of the invention.

The present invention thus relates to a mechanical safety and ignition function for such tools that are driven by combustion gases from a power unit containing a propellant charge initiated by an integral percussion primer that is in turn activated by a firing pin incorporated in a spring-driven ignition piston, which is locked in cocked position by a releasable catch with the piston spring cocked, and which is triggered by the catch being actuated to release the ignition piston whereby the ignition piston and firing pin are propelled forwards by the piston spring until the tip of the firing pin impacts with the percussion primer.

The problem with such an ignition device is to achieve a device that can only be triggered when the tool is ready for initiation, but which can still be triggered under all conditions even when the operator is wearing thick gloves.

We have resolved this problem by employing a trigger that is manoeuvrable in two separate directions to operate the catch. The two directions of motion of the trigger form in effect a right angle relative to each other, and both motions must be performed in a direct sequence, and this can only be performed if other parts of the tool are correctly positioned relative to each other. (It must be possible, namely, to open the cutter relatively easily to prime it with the power unit necessary for initiation.) In our invention we have decided to assign the first motion along the axis of the cutter handle with the second motion radially in towards the central axis of the handle. This combination of movements can namely be carried out even when wearing thick gloves, and no normal external damage can reasonably result in the same movement pattern. The trigger is normally held by a spring in such a position that the trigger is engaged with a dedicated locking face on the handle, as well as lying directly above the axis around which the catch must pivot for it to release its engagement in the recess in the ignition piston while the piston spring of the cutter is cocked.

The present invention is defined in the subsequent Patent Claims and shall now be described in further detail with reference to the appended figures in which Figure 1 shows a gas-powered cutter;

Figure 2 shows the operating unit of the cutter and the external handle to a larger scale, and Figure 3 shows a longitudinal section through the operating and handle units illustrated in Figure 2.

The cutter in question consists of a jaw 1 comprising a U-shaped section 2 that ends with a bucker 3, the opposite end being in the form of a holder in which a cylinder 4 is mounted. A displaceable cutting blade 5 is arranged inside the jaw 2 with the blade facing the bucker 3. When the cutter is triggered the cutting blade 5 is propelled against the bucker 3 by the ignition piston 16 which is longitudinally displaceable in the cylinder 4. The combustion gases from the power unit are utilised as propellant for the piston unit. The design of the piston unit, jaw and cutting edge are not part of the present invention and, consequently, will be left open in the following description. These parts are described in detail in Swedish patent application number 9901169-4.

The cutter also comprises an operating unit 6 which, at the opposite end from the bucker, terminates in a tubular shaped handle 34.

The operating unit 6 is attached to the cylinder 4 by the wishbone arm 7 extending from the guide sleeve 11, and the operating unit can be locked relative to the cylinder by a rotatable aft closure 8 that is in turn integral with the main tubular section of the operating unit. The wishbone arm 7 anchors the jaw and cylinder of the cutter with the operating unit, but also enables the latter to be hinged downwards as soon as the aft closure 8 is in openable position. The aft closure 8 has a bayonet . fitting 9 by means of which it and the complete operating unit can be coupled to the jaw and cylinder by a rotation movement of the handle 34. The hinged opening feature is necessary to enable a power unit 23 containing propellant to be inserted into its chamber in the cylinder 4 (see Figure 2). The aft closure 8 in turn constitutes an integral part of the main tubular section 10 of the operating unit 6. The aft closure 8 is rotatable in a guide sleeve 11 from which the wishbone arm 7 extends. A trigger 12 is movably mounted in the guide sleeve 11. The trigger 12 can be displaced axially in the direction of arrow A by the force of a trigger spring 13 and, under certain conditions, the end of trigger 14 furthest from the trigger spring 13 can also be displaced radially in the direction of arrow B a limited distance towards the centre of the guide sleeve 11 via a dedicated opening 11a. This end of the trigger furthest from the trigger spring is designed with a tongue 12a that prevents the trigger 12 from being operated in this radial direction until the trigger has been displaced a sufficient distance axially in the direction of arrow A. The functioning of the trigger will be dealt with later.

There is a piston spring 15 arranged inside the main tubular section 10 of the ignition piston 16. A firing pin 17 is also located in the ignition piston 16. In the front section of the latter there is a recess 18 in which a coil spring 19 is arranged. In uncocked position the said coil spring projects slightly in front of the ignition piston 16 (in its direction of motion), and between the ignition piston and the front end- wall 20 of the space 21 in which the said ignition piston is displaceable there is a moveable sleeve 22 located around the rear part of the firing pin 17. The task of the sleeve 22 is to retain the ignition piston 16, and thereby even the firing pin 17, in general uncocked mode while also enabling the firing pin to strike and initiate the percussion primer of the power unit 23 that is adjacent to the impact position of the firing pin when the ignition piston 16 is propelled forwards by the force of the percussion spring 15. In the version described it is assumed that the power unit 23 is arranged centrally between the projections with which the bayonet fitting 9 is designed to engage.

Figure 3 illustrates a rear damper 24 made of hard polyurethane that functions as a damper and piston spring guide. The said rear damper is located inside the piston spring 15. The main tubular section 10 terminates in a handle nut 25. When cocked the cutter is held in ready-to-trigger mode by the action of a catch 27 that pivots on a pin 26 that functions as follows. Catch 27 incorporates a pawl 28 that interacts with different recesses in the ignition piston 16 depending on the position of the ignition piston. In Figure 3 the said ignition piston has two recesses 29 and 30, of which recess 29 is the uncocked position which cannot provide sufficient force to propel the firing pin 17 to initiate the percussion primer if the cutter is triggered, while recess 30 is the position in which the ignition piston is cocked ready for initiation. The opposite end of catch 27 from pawl 28 incorporates an actuator 31 in front of pin 26. A blade spring 32 also acts on catch 27 to press pawl 28 down to engage with either of recesses 29 or 30 in ignition piston 16.

Catch pin 26 is mounted in holder 33 that is fixed to the main tubular section 10 of the operating unit 6.

The tube shaped handle 34, which has its own return handle spring 35, is used to cock piston spring 15. When handle 34 is pulled in the opposite direction to the bucker 3 the handle actuates ignition piston 16 via a transfer screw 36 in the direction that cocks piston spring 15, and the ignition piston is held in ready-to- trigger mode by the pawl 28 of catch 27 engaging in recess 30.

To enable the cutter to be triggered it is necessary in the first instance for a power unit 23 to have been inserted, in the second instance for bayonet fitting 9 to be completely closed, in the third instance for piston spring 15 to be cocked with the pawl 28 of catch 27 engaged in recess 30 in ignition piston 16, in the fourth instance for the previously described trigger 12 to be displaced axially in the direction towards the bucker 3, and in the fifth instance for trigger 12 to be depressed radially inwards, whereby it pivots around pin 12b and actuates the actuator 31 of catch 27 and thereby causes the catch to pivot against the force of blade spring 32 so that pawl 28 disengages with recess 30 to release ignition piston 16.

If trigger 12 is not displaced axially it cannot actuate the catch actuator 31 as the trigger is then directly above catch pin 26, and the trigger tongue 12a is also above the front edge of handle 34 thus preventing any radial movement of the trigger tongue.

Another vital condition that must be met to enable the cutter to be triggered is that bayonet fitting 9 is correctly positioned, otherwise the trigger 12 mounted in guide sleeve 11 on the main tubular section 10 and those parts that are rotated together with it will be wrongly positioned to the side of catch 27 and opening 11a.

More detailed information is contained in the following functional description of how to operate the cutter.

Initial position: cutter closed with uncocked trigger mechanism open the cutter by rotating operating unit 6 in the handle 34 counter-clockwise

90 degrees to the stop and hinge down the operating unit insert a power unit 23 into the cartridge chamber (which is only implied in

Figure 3) on the cylinder 4 section close the cutter by hinging up the operating unit 6 and rotate the handle 34 clockwise 90 degrees to the stop whereby a snap catch engages (refer to reference 41 on Figure 2 regarding the snap catch function) cock the trigger mechanism by pulling the handle 34 rearwards to the stop and then release it back to initial position trigger the cutter by using the thumb of the hand holding the handle 34 to slide the trigger 12 forwards while simultaneously pressing it down.

If no cut is made after priming and cocking the cutter: open the cutter and remove the power unit 23, close the cutter and trigger it.

Function

When the cutter is opened the firing pin and ignition piston are forced to their uncocked position with the ignition piston locked in uncocked position 29 by the fact that stop 39 in the ignition piston 16 operates against a curve section 40 on the guide sleeve (see 11 on Figure 2). The firing pin 17 is mounted in the ignition piston 16 at the front of which there is a spring-loaded sleeve 22. This arrangement also keeps the firing pin 17 in uncocked position. Stop 39 - a pin mounted in the ignition piston 16 - is visible from the outside and thus enables the status of the trigger mechanism to be ascertained.

The cutter is primed and closed, after which the operating unit 6 is kept closed by a snap catch 41 between guide sleeve 11 and the main tubular section 10.

The trigger mechanism is cocked by pulling the handle 34 rearwards whereby the transfer screw 36 takes the ignition piston 16 with it, and this compresses the piston spring 15. When the ignition piston reaches the cocked position it is secured by engaging with catch 27. This is achieved by pawl 28 on the catch engaging with recess 30 in the ignition piston under the force exerted by blade spring 32. This feature is self-locking.

The ignition piston has two recesses, 29 and 30. If the trigger mechanism is tensioned insufficiently to cock it, pawl 28 then engages in recess 29 instead. This position has inadequate spring force to initiate the cutter. If, for example, one should lose one's grip on handle 34 while cocking the trigger mechanism, then pawl 28 safely engages in recess 29 in the ignition piston 16.

To initiate the cutter, the trigger 12 must first be pushed forwards in the direction of arrow A. A load is exerted on the trigger by trigger spring 13, which means that a certain force is required to move the trigger. When in forward position the trigger needs to be pressed downwards with a certain force, which is transferred to the actuator 31 of catch 27, the centre of which is pivoted. The force applied works as a lever in relation to the pivot, creating a torsional moment that lifts pawl 28 from recess 30 in ignition piston 16.

If the trigger 12 is not pushed forwards no lever effect is obtained and the cutter cannot be initiated. When released the ignition piston 16 is propelled forwards by the force from piston spring 15. Sleeve 22 - at the front of the ignition piston - hits the impact face inside main tubular section 10. Spring 19 between the sleeve and the ignition piston is compressed causing the ignition piston to impact with the sleeve thereby causing the firing pin 17 to reach its foremost position where it impacts with the percussion primer in power unit 23, thus causing its propellant charge to initiate.

After initiation, spring 19 in ignition piston 16 returns sleeve 22 and firing pin 17 to uncocked position.

Safety

There is a double safety feature whereby hazard initiation is prevented during priming as the firing pin is forced to uncocked position when the cutter is opened, and initiation is only possible if the cutter is completely closed.

Two conditions have to be met (push forwards + press down) to be able to initiate the cutter.

Claims

PATENT CLAIMSWe hereby claim and desire to secure by Letters Patent the following.

1. A mechanical safety and trigger mechanism for tools powered by combustion gases from a propellant-charged power unit (23) of a type initiated by an integral percussion primer that is activated by a piston spring (15) driven firing pin (17) which, via a manoeuvrable catch (27) can be engaged in ready-to-trigger mode with the piston spring (15) cocked, and which is initiated by a catch (27) or equivalent being forced out of its pawl engagement when actuated manually e rein the said trigger (12), in order to be able to actuate catch (27) so that it lifts out of its engaged position, is arranged to enable it to be displaced in two consecutive principally mutually perpendicular directions (A and B) of which the first motion (A) is necessary to enable the second motion (B), while the second motion (B) actuates catch (27) in the desired direction.

2. A mechanical safety and trigger mechanism as claimed in Claim 1 wherein the motion of the trigger (12) in the first direction (A) must overcome the force exerted by the first spring (13), and the motion of the said trigger in the second direction must overcome the force of the second spring (32) acting on catch (27) in the direction of its engaged position.

3. A mechanical safety and trigger mechanism as claimed in Claim 1 or 2 wherein the trigger (12) is pressed by the first spring (13) into a position whereby its motion in the second direction (B) is prevented by the fact that the said trigger is located directly above the pivot pin (26) around which catch (27) pivots from its engaged position to its disengaged position.

4. A mechanical safety and trigger mechanism as claimed in any of Claims 1-3 wherein catch (27) is incorporated together with piston spring (15) and firing pin (17) etc in an inner tubular section (10) that is pivotably arranged in an outer sleeve (11), and whereby the trigger (12) and its spring (13) are incorporated in the outer sleeve (11) while the catch (27) is incoφorated in the inner tubular section (10), and whereby the trigger (12) is displaced out of reach of the catch (27) as soon as both the inner tubular section (10) and the outer sleeve (11) are rotated relative to each other.

5. A mechanical safety and trigger mechanism as claimed in Claims 1-4 wherein the firing pin (17) that initiates the percussion primer of the power unit (23) constitutes an integral part of a displaceable ignition piston (16) on which the piston spring (15) acts, and whereby between the front end of the said ignition piston and the front end of the space in which it is displaceable there is a coil spring (19) whose force is designed to restrain the firing pin (17) from contact with the percussion primer of the power unit (23) under all conditions excepting when the ignition piston and firing pin are triggered to move forwards towards the percussion primer.

6. A mechanical safety and trigger mechanism as claimed in Claim 5 wherein between the coil spring (19) located in the front end of the ignition piston (16) and the front wall of the space in which the said ignition piston is displaceably arranged there is a displaceable sleeve (22) located around the firing pin (17).