EP0798084B1 - Fastener driving tool with automatic return of plunger to firing position - Google Patents

Abstract

The gun drives a plug (6) for fixing a part to a support by a plunger weight (10). The plunger is propelled to the front of the gun (9) under the action of combustion gases from a cartridge (11) located in a gun combustion chamber (15). A return chamber, along the plunger, has a front space (30) closed by the plunger front surface (28) and a rear space (22). Both spaces are in communication during displacement of the plunger. The rear space, after a first displacement of the plunger to the front, communicates with the combustion chamber. After communication between the front and rear spaces, the rear space is isolated from the front space after a second displacement towards the front of the plunger. Following this, the rear space communicates with the outside of the gun. The combustion gas expansion is trapped in the front space and returns the plunger to the rear firing position.

Description

The present invention relates to a tampon driving apparatus for fixing a part to a support material, by means of a counterweight arranged to be propelled forward in a barrel under the action of combustion gas from a cartridge disposed in a barrel combustion chamber and comprising, along the counterweight, a reminder chamber with an anterior space closed by a surface front of the counterweight and a posterior space arranged for, after a first movement towards the front of the counterweight, communicate with the combustion chamber, for then, and after communication of the two spaces, be isolated from the previous space and the counterweight is pulled back into the barrel.

We already know such a device by European patent EP-A-022 37 40. But in the apparatus of this document, the isolation of the two posterior spaces and earlier can only intervene after relative displacement of a socket for guiding the buffer and a support tube, that is to say either during a backing up the appliance or if the appliance is fitted with a cylinder head which can back off under the action of combustion gases. If the operator is the camera firmly during firing, the camera will not back down and providing a device with a movable cylinder head is not very simple. In addition, without recoil from the device or cylinder head, the gas pressures in the two anterior and posterior spaces are balanced, without any exhaust gases to the outside of the device, so that the flyweight takes any position.

The present invention aims to simplify such an apparatus in order to eliminate the aforementioned drawbacks.

To this end, the invention relates to an apparatus of the type defined above and characterized according to either of independent claims 1 and 4.

In the apparatus of the invention, it is therefore the flyweight and nothing but the counterweight which acts as a valve with, as a result, a guaranteed return in firing position of the counterweight.

Other features are described in dependent claims 2, 3 and 5, 6, respectively.

In one case, the internal communication groove of the barrel may extend axially over a length equal to the difference between the second displacement and intermediate displacement of the raised flyweight the axial thickness of the counterweight head.

More preferably, the barrel combustion chamber is extended in a nozzle projecting forward and arranged to enter the rear skirt of the flyweight head.

In the other case, the counterweight may include a head extended by a appendage protruding rearward and arranged to enter the combustion chamber.

Note that the US patent US-A-2877750 teaches a device which presents certain analogies with that of the present application but of which the interest relates to its mechanism of damping of different weights a counterweight return mechanism.

• la figure 1 est une vue en coupe axiale de la première forme de réalisation de l'appareil, juste avant la mise à feu ;
• la figure 2 est une vue analogue à la figure 1, la masselotte en position intermédiaire ;
• la figure 3 est une vue analogue aux précédentes, après retour incomplet de la masselotte et avant sortie d'appui de l'appareil,
• la figure 4 est une vue en coupe axiale de la deuxième forme de réalisation de l'appareil, juste avant la mise à feu ;
• la figure 5 est une vue analogue à la figure 1, la masselotte en position intermédiaire et
• la figure 6 est une vue analogue aux précédentes, juste avant retour de la masselotte.

The invention will be better understood with the aid of the following description of two embodiments of the apparatus, with reference to the appended drawing, in which

• Figure 1 is an axial sectional view of the first embodiment of the apparatus, just before firing;
• Figure 2 is a view similar to Figure 1, the weight in the intermediate position;
• FIG. 3 is a view similar to the preceding ones, after incomplete return of the counterweight and before the support outlet from the device,
• Figure 4 is an axial sectional view of the second embodiment of the apparatus, just before firing;
• FIG. 5 is a view similar to FIG. 1, the counterweight in the intermediate position and
• Figure 6 is a view similar to the previous, just before return of the weight.

The apparatus of Figures 1 to 3 comprises, integral with a handle 1, a device firing 2, a percussion device 3, means, not shown, receiving and driving here a disc 4 cartridge loader 11 and a set 5 for driving a fixing pad 6 in a material support 7.

The drive assembly 5 comprises, in a cylindrical tube 8, mounted in the handle, a barrel 9 with an axis 20, in the barrel 9, a counterweight 10, screwed into the front of the barrel, a guide support 12 and, in the support 12, a buffer guide 13.

At the front of the barrel and at the rear of the guide support 12 is arranged a member 29 for amortization of the counterweight.

At the rear of the barrel 9 is a combustion chamber 15 which is extends into an internal sleeve 16, in the form of a nozzle, projecting towards the front in the main part of the barrel.

The counterweight 10 comprises a head 17, a front rod 18 and a skirt posterior 19 inside which the inner sleeve 16 of the barrel can enter.

A plurality of axial grooves 21 are provided at the inner periphery of the barrel 9, in one place and over a length which will appear further on. The rear skirt 19 of the counterweight has an external lateral recess annular 22, so that the outer diameter of the skirt is smaller than the diameter of the head 17 and this skirt is pierced, in its rear part, with a passage 23. There could also be several passages.

The barrel also has a longitudinal annular external lateral recess 24 opening, on the one hand, into the bore of the barrel by a passage 25 pierced in the rear part of the barrel 9, here in the axial length of the nozzle 16, and, on the other hand, outside the device when it is in the open position by through a passage 26, drilled in the cylindrical tube 8 gun holder, and a longitudinal annular external lateral recess 27 formed on the tube 8.

As so spared, the barrel and the flyweight define a return of the flyweight along the flyweight, in this case around it, with an anterior space and a posterior space.

The anterior space 30 is formed between the counterweight rod 18 and the part of the barrel in front of the grooves 21; it is closed by the anterior frontal surface 28 of the flyweight head 17.

The posterior space is formed essentially by the annular recess 22 around the counterweight skirt 19.

The rear space 22 of the reminder chamber can communicate with the combustion chamber 15 through passage 23 and the two front spaces 30 and posterior 22 can communicate with each other through the barrel grooves 21.

Device operation

The barrel 9 can slide in the barrel-carrying tube 8 between a front position, in abutment against a washer 31 at the bottom of a ring 32 screwed onto the tube 8, and a rear position, pressing against a front stop 33 of the housing of the charger 4.

The counterweight 10, by a tapered front portion 34 of its rod 18, can slide in the bore of the buffer guide 13.

By its head 17, it can slide in the barrel 9 and, by the skirt 19, on the inner sleeve 16 of the barrel. The buffer guide 13, under or against the action of a spring 14, can slide in its support 12 between the member damping 29 and the front bottom 35 of the support 12.

After inserting a fixing pad 6 into the pad guide 13 and placing cartridges 11 on the magazine 4, the device is pressed against the support 7. The buffer guide 13 slides backwards, compresses the spring 14, abuts against the damping member 29 and thus drives the barrel 9 backwards which activates the firing system 2 and positions a cartridge 11 in the combustion chamber 15.

After ignition, the gas pressure rises in the nozzle 16 and the counterweight 10 is thus propelled forward. When the posterior surface 36 of the flyweight head 17 has traveled a first distance I and therefore that the passage 23 of its rear skirt 19 arrives at the right of the front end of the nozzle 16, the gases under high pressure, through the passage 23, begin to escape from the combustion chamber to the rear space 22 of the reminder chamber. The flyweight continuing its course, when the surface rear 36 of the flyweight head 17 arrives at the right of the rear ends grooves 21, the two front 30 and rear 22 spaces are set communication. All available highly compressed gases are controlled towards space 30. At this time, the flyweight has traveled, since the beginning of its displacement, an intermediate distance. Referring especially to the figure 2, it will be noted that this intermediate distance is only very slightly greater than the first distance I. We could also imagine that these two distances are equal. The combustion gases then escape towards the front space 30 and this, until the counterweight has traveled, from the start of its propulsion, a second distance and that the surface anterior frontal 28 arrives at the right of the front ends of the grooves 21 and that the flyweight therefore isolates, like a valve, the rear space 22 of the anterior space 30.

It will be noted here that the grooves 21 extend axially over a length equal to the difference between the second displacement and the displacement intermediate of the counterweight increased by the axial thickness of the head of counterweight 17.

The flyweight continues to run forward, compressing the trapped gases in the anterior space 30, until, first, the posterior skirt of counterweight 19 clears the passage 25 drilled in the barrel and authorizes the evacuation of gases from the posterior space 22 to the atmosphere then, by the clean energy of the counterweight, that the buffer 6 is fixed in the support 7 (figure 3).

Under the pressure of the gases in the anterior space 30, the counterweight is then recalled to the rear in the firing position, the return being facilitated by the communication of the posterior space 22 with the exterior of the device.

After the counterweight 10 has returned to a position in which the passage 23 in the rear shoe skirt 19 is again closed through the nozzle 16, part of the gases of the posterior space 22 continues to escape through passage 25 in the barrel but an air mattress is formed at the rear of the counterweight which can significantly slow its return.

When the device comes out of support, the spring 14 recalls the buffer guide 13 and the barrel 9 forwards and the magazine 4 advances by one step and the buffer guide comes occupy a position in front of the weight rod portion 18 no tapered.

Thanks to return balls 37 in the buffer guide 13 and a ring 38 in the guide support 12, when the device is resting again, the ring 38 being moved slightly backwards to push the balls 37 against the tapered portion 34 of the counterweight rod then against the shoulder annular 39 between the two rod portions, the counterweight 10 is driven completely back until it comes into contact with the disc charger 4. As soon as the rear end of the ring comes into abutment against the damping member 29, it is pushed forward which has the effect releasing the pressure of the balls 37 on the counterweight rod.

The variant embodiment of the apparatus of FIGS. 4 to 6 is not distinguished from the first embodiment of Figures 1 to 3 as a whole 5. The flyweight 50 has an extended head 51, towards the front, by a rod 52 with a tapered front portion 53 and, towards the rear, by a appendage 54 of section narrowed relative to that of the head 51.

At the rear of the barrel 9 is disposed a cartridge holder 55 of internal section, at the front of the cartridge housing 56, substantially equal to that of the flyweight appendage 54. But this cartridge holder and the barrel could also be self-contained.

In front of the cartridge holder 55, the barrel wall 57 has a extra thickness in the plane of which the inner section of the barrel is equal to that of the cartridge holder 55 and forming with the front barrel part 58 a annular shoulder 59 of stop of the counterweight head 51.

In the barrel wall, extending partly into the portion of small thickness 58 and partly in the extra thickness portion 57, is provided a passage 62 opening into the bore of the barrel, at the front, through an opening anterior 60 and, at the rear, by a posterior opening 61. As in the other embodiment, the barrel has an external lateral recess longitudinal annular 63 opening and into the bore of the barrel, by a passage 64 in the barrel, and outside the device, by passage 65 in the barrel holder 8.

The return weight chamber here also includes an anterior space 66, at the front of the counterweight head 51 and its front surface 68, and a posterior space 67 here constituted by the communication passage 60 - 62 the along the counterweight 50. It will be noted that the axial length of the passage 62, at the dimension of the openings 60, 61 close, is here substantially equal to the sum of the axial lengths of the flyweight head 51, of the bore of the cartridge holder 55 and double the axial length of the excess thickness of canon 57.

After firing - from pressing down to firing, the operation is identical to the previous one - the gas pressure rises in the cartridge housing 56 and the flyweight 50 is propelled forward.

When the rear end of the flyweight appendage 54 has traversed a first distance equal to the axial length of the inner bore of the cartridge holder 55, he discovers the posterior opening 61 of the passage 62 which puts in communication the anterior space 66 and the posterior space 67 of the booster chamber with combustion chamber 56.

The flyweight 50 continues to run forward and, when the head of counterweight 51 arrives at the right of the anterior opening 60 of passage 62, the flyweight having traveled, since the start of propulsion, one second distance, the counterweight head 51 closes the anterior opening 60, which isolates posterior space 67 of anterior space 66.

As before, the flyweight continues to run forward while compressing the gases trapped in the anterior space 66 until the buffer. So, under the pressure of the gases in the anterior space 66, and thanks to the exhaust of gases from the posterior space 67 towards the outside, the counterweight is recalled backwards. Its complete return to the firing position is guaranteed, always as before, by the ring 38 and the balls 37.

In the first embodiment of Figures 1 to 3, the air mattress, formed at the rear of the counterweight after its return to the rear, under the action of balls 37 and ring 38, is compressed into a corresponding volume substantially to that of the inner bore of the nozzle 16. In the second embodiment of Figures 4 to 6, the mattress at the rear of the counterweight is compressed into a volume corresponding substantially to that of the housing cartridge 56, much smaller than that of the inner bore of the nozzle 16 of the first embodiment. To reassemble the flyweight completely backwards, so you have to provide, with the second form of achievement, a greater effort than with the first embodiment. The weight of the second embodiment will therefore be more likely to set out forwards.

Claims (6)

1. Apparatus for driving a plug (6) for fixing a piece to a support material by means of a weight (10) arranged to be propelled forwards in a barrel (9) under the influence of combustion gas of a cartridge (11) arranged in a combustion chamber of the barrel (15) and including, along the weight, a return chamber with a front space (30) closed by a frontal surface (28) of the weight (10) and a rear space (22) arranged, after a first forwards displacement of the weight (10), to communicate with the combustion chamber (15) to then, and after the two spaces (30, 22) have been placed in communication, be isolated from the front space (30) and for the weight (10) to be returned towards the rear in the barrel (9), characterised by the fact that the two front (30) and rear (22) spaces communicate with each other during the displacement of the weight (10) and the rear space (22) is isolated from the front space (30) after a second forwards displacement of the weight (10) following which, the rear space (22) communicating with the outside of the apparatus, the expansion of the combustion gases trapped in the front space (30) returns the weight (10) towards the rear into the firing position, the return chamber (30, 22) being directly arranged between the weight (10) and the barrel (9), the weight (10) including a head (17) provided with a rear skirt (19) at the outer periphery of which is arranged the said rear space (22) and which has passing through it at least one passage (23) for communication between this rear space (22) and the combustion chamber (15) and the barrel (9) being provided at least with an internal groove (21) for communication, after an intermediate displacement, between the two front (30) and rear (22) spaces.
2. Apparatus as described in claim 1, in which the internal communication groove (21) of the barrel (9) extends axially along a length equal to the difference between the second displacement and the intermediate displacement of the weight (10) plus the axial thickness of the weight head (17).
3. Apparatus as described in one of claims 1 and 2, in which the combustion chamber (15) of the barrel (9) is extended into a forwardly projecting nozzle (16) arranged to be introduced into the rear skirt (19) of the weight head (17).
4. Apparatus for driving a plug (6) for fixing a piece to a support material, by means of a weight (50) arranged to be propelled forwards in a barrel (58) under the influence of combustion gas of a cartridge (11) arranged in a combustion chamber of the barrel (55, 56) and including, along the weight, a return chamber with a front space (66) closed by a frontal surface (68) of the weight (50) and a rear space (61) arranged after a first forwards displacement of the weight (50), to communicate with the combustion chamber (55, 56) to then, and after placing in communication of the two spaces (66, 61), be isolated from the front space (66) and for the weight (50) to be returned towards the rear in the barrel (58), characterised by the fact that the two front (66) and rear (61) spaces communicate with each other during the displacement of the weight (50) and the rear space (61) is isolated from the front space (66) after a second forward displacement of the weight (50) following which the rear space (61) communicating with the outside of the apparatus, the expansion of the combustion gases trapped in the front space (66) returns the weight (50) towards the rear into the firing position, the rear space of the return chamber including, formed in the barrel (58), a passage (62) for communication between the combustion chamber (55, 56) and the front space (66) and the weight head (51) being arranged, after the said first displacement, to uncover a rear opening (61) of the passage (62) of the barrel (58) and, after the said second displacement, to block a front opening (60) of the said passage (62).
5. Apparatus as described in claim 4, in which the axial length of the communication passage (62) is substantially equal to the sum of the axial lengths of the weight head (51), of the bore of the cartridge holder (55) and of double the axial length of an extra thickness of the barrel (57).
6. Apparatus as described in one of claims 4 and 5, in which the weight (50) includes a head (51) extended by a rearwardly projecting appendage (54) arranged to be introduced into the combustion chamber (55, 56).

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