GB2149337A - Fastener driving apparatus - Google Patents

Abstract

Fastener driver apparatus having a reciprocating piston (20) driving fasteners via a rod (34). Manual trigger (27) operates valve (16) to drive a single fastener. One operation causes piston (20) to reciprocate once as a result of pawl (26) disengaging from valve rod (16). An adjustment block (32) allows different piston strokes to be set. By mounting trigger (27) on block (32) separate adjustment of the trigger (27) and pawl (26) is unnecessary. <IMAGE>

Description

SPECIFICATION Fastener driving apparatus This invention relates to a fastener driving device comprising a body member; piston means mounted in said body member for reciprocating movement between a first posi tion and a second position; drive means hav ing an actuating member and operable to drive said piston means from the second position to the first position when the actuating member is in a normal position and operable to drive said piston means from the first position to the second position when the actuating member is in an actuated position; stop means which is adjustable to adjust said second position of the piston; triggering means operable to move from a rest position to a triggering position thereby moving said actuating member to its actuated position; and release means to release said actuating member to allow it to return to said normal position with the triggering means remaining in its triggering position. The device allows the piston mcans to make a complete reciprocal operation by one operation of the triggering means.

When fasteners, such as staples, are inserted into corrugated cartons for holding the flaps closed the proper amount of clinch is important. Should the staple legs be bent inward too much the legs will cut or break the corrugated fiber and result in a weak closure.

Likewise if the legs are not folded inward enough the result is a loose or an easily opening closure.

A common practice is to cause a pistonoperated driver and folding elements to make an exact stroke each cycle. This is achieved by having the piston or driver bottom out on the stop means within the tool. The stop means is usually adjustable since the corrugated thickness and strength vary. By actuating the actuating member (e.g. a valve lever) the piston will make a downward stroke. Releasing the actuating member causes the piston to reverse thereby producing a properly clinched staple.

Should the operator release the trigger too soon then a partial cycle will occur resulting in a poorly clinched staple. To prevent this from happening the operator tends to hold the lever upward for a longer time, making the cycle unnecessarily long. The packaging operation is inconsistent and slow as a result.

For faster operation of pneumatic tools, different devices have been in use to give a complete reciprocal cycle by operating the valve lever in only one direction, commonly known as a "cycle through" action. To cause reversal of the actuating member at the same time as the piston bottoms out on the stop means is in any case difficult, but is especially difficult when the stop means is adjustable.

To operate the actuating means during the stroke of the piston usually results in an inconsistent stroke of the piston. Attempts have been made to provide for adjustment of the cycle through mechanism each time the stop means is adjusted but this is time consuming and often leads to inaccurate adjustment.

An object of this invention is to provide a fastener driving device having a piston means, a cycle through mechanism and means for adjusting piston means travel without necessitating separate readjustment of the cycle through mechanism.

According to the invention, this object may be achieved in that said triggering means is mounted on said stop means and in that said release means is arranged for actuation by said piston means with the piston means at a predetermined position relative to said stop means.

Another object of the invention is to provide a consistent driving action on each cycle of the tool.

Although the invention is applicable to devices for driving fasteners such as staples used for clinching, the concept of the invention is also applicable to tools that drive fasteners directly into a workpiece where penetration depth must be controlled. Such tools may be applied to attaching a fragile material to a wooden base.

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a cross-sectional view of a fastener driving device according to a first embodiment of the invention; Figure 2 is a cross-sectional view of said first embodiment starting a driving stroke; Figure 3 is a cross-sectional view of the first embodiment with a piston at full stroke; Figure 4 is a cross-section along the plane IV-IV of Figure 2 showing air passages; Figure 5 is similar to Figure 1 but with a stop means in a different position; Figures 6 and 7 are detailed views of a release mechanism in the embodiment of Figure 1; Figure 8 shows a cross-sectional view of a second embodiment of the invention; Figure 9 is a further cross-sectional view of the second embodiment;; Figure 10 is a plan view of details of the second embodiment; Figure 11 is a cross-sectional view of a third embodiment of the invention; and Figure 1 2 is a cross-sectional view similar to Figure 11 with the piston at full stroke.

Figures 1 to 7 show a first portable pneumatically operated driver tool for driving fasteners equipped with a manual triggering device. Referring to Figure 1, the tool has a body 1 5 to which compressed air is con nected at 14 to provide a power source for driving a piston 20. A valve stem 16 is biassed down to a normal "at rest" position by a spring 1 7. The air therefore passes through passages 18, 19 and 35 to fill a chamber 39 under the piston 20 thus holding the piston 20 in the uppermost position. A chamber 21 above the piston 20 is sealed off by an "0" ring 22 and is open to atmosphere through a passage 38 into a sleeve 24 and through a passage 23 to the outside of sleeve 24, the air then passing along the outside of the sleeve 24 and emerging through apertures 25 and 26 into passage 37.Passages 23 and 38 are shown more clearly in Figure 4.

The sleeve 24 is sealed in position within the body 1 5 becoming effectively a part thereof. The use of a sleeve secured within a body is not the only method of forming air passages. It is well known in the art that such passages can also be cored or machined.

Although the valve stem 1 6 is shown biassed by a spring 17, it is common knowledge the valve stem could also be pneumatically imbalanced to accomplish the same positioning effect. The spool-type valve described herein is for convenience of illustration only and does not constitute any limitation upon the scope of the invention.

A trigger lever 27 has two lateral spaced flange portions for accepting transversely disposed pins 28 and 29.

A release element constituted by pawl 26 is pivotally mounted between the flange portions for pivoting about the pin 28. A torsion spring 30 mounted on pin 29 creates a counterclockwise moment on the pawl 26 to bias the pawl 26 against the pin 29. This maintains the top portion of the pawl 26 under the end of the valve stem 1 6 when the trigger is released (Figure 1) thereby ensuring that the valve stem 1 6 is moved upward as the trigger lever 27 is pulled against the bias of spring 30.

The trigger assembly containing the trigger lever 27, pawl 26, pins 28, 29 and the torsion spring 30 is pivotal about a pin 31 located on an adjustment block 32 forming a piston stop. The trigger assembly therefore moves in conjunction with vertical adjusting movement of the adjustment block 32 when the stroke is changed. The adjustment is made by turning the adjustment screw 33. As the screw 33 is turned clockwise, the adjustment block 32 is moved upward e.g. to the position shown in Figure 5 thereby shortening the stroke of the piston 20. This in turn limits the distance by which the driving member 34 can be forced downwards.

Referring to Figure 2, the trigger 27 has been lifted, pivoting about pin 31, thereby raising the pawl 26. As the pawl 26 is moved upward, it engages the valve stem 16 which is thereby raised against the return spring 1 7.

When two "0" rings 36 pass over the respective passages 1 9 and 38, the air flow within the cylinder chambers 21 and 39 is reversed, as follows: The compressed air in the lower chamber 39 flows through passages 35, 19, 26A and 37 to atmosphere. The inlet air supply can flow through passages 18 and 38 into the top cylinder chamber 21 forcing the piston 20 and driving member 34 downwards. The "O" ring seal 22 on the piston 20 contains the air to give the maximum downward thrust. The "0" ring seals referred to and shown in this specification are used for ease of description, but does not limit the type of seals to "O" ring. Other types of seals, such as cup, molded, square, etc., could also be used and the invention is not limited to one style only.

As shown in Figure 3, when the piston 20 has completed its full downward stroke, it strikes the adjustment block 32 and depresses a pawl trip rod 40. Rod 40 then acts upon one end of the pawl 26 thereby rotating this member clockwise about the pivot pin 28.

This pivoting action by the pawl 26 disengages the upper portion of the pawl 26 from the valve stem 16 thereby allowing the return spring 1 7 to force the valve stem 1 6 downwards to its normal position. After the seals 36 on the valve stem 1 6 have moved past the passages 19 and 38 respectively, the direction of air flow again is reversed, so that air escapes from the upper cylinder chamber 21 and compressed air enters the lower cylinder chamber 39. Thus the piston 20 and drive rod 34 return to their original positions. All the above action constitutes a "cycle through" action since it occurs during the time in which the trigger 27 is pulled upward and held momentarily.

It is unnecessary to release the trigger 27 before the piston 20 and driving member 34 will return to the original position ("non-cycle through").

Figures 6 and 7 show the pawl trip rod 40 having been released by the piston 20 and having been forced upwards by a rod return spring 41. The trip rod 40 is contained by a retaining clip 42. An "0" ring seal 43 is used to resist air leakage around the trip rod 40 and the adjustment block 32. Although the pawl 26 has been released by the trip rod 40, the torsion spring 30 can rotate the pawl 26 about the pivot pin 28 only until the top portion rests against the side of the valve stem 16. As shown in Figure 6, the trigger 27 must now be released to allow the pawl 26 to clear the end of the valve stem 1 6 before it can rotate to its original position.

This ensures safe driving of only one fastener at a time. Thus, one trigger depression can lead to only one reciprocation of the piston 20 and the driving of only one fastener. If the tool were to be allowed to rapidly drive fasteners with only one trigger 27 depression, the tool would exhibit a dangerous "machine gunning" effect.

Since the trigger 27, and consequently the pawl 26, spring 30, and pin 28 are attached to the adjustment block 32 and move together therewith, the relationship between the trip pin 40 and pawl 26 is substantially unchanged when a stroke adjustment is made. The pawl pivot pin 28 is located such that the trip pin 40 must be nearly fully depressed before pawl 26 will release the valve stem 1 6 regardless of the position of the adjustment block 32. The pawl slips from under the lower portion of the valve stem 1 6 when the piston 20 depresses the trip pin 40 at the end of the stroke.The design allows for possible variation in manufacturing tolerances and may even trip a short distance before piston 20 actually strikes the adjustment block 32, but the momentum will carry the piston 20 and driving member 34 this small distance to achieve the desired constant stroke as set by the adjustment block 32.

Referring now to Figure 8 and Figure 9, a second fastener driving device embodiment is shown having an alternative valve tripping device. The trigger 46 is pivotally mounted on the adjustment block 32 as previously described. A trip plate 47 is slidably mounted within the trigger 46 and has flanges 55 (Figure 10) extending through the lateral flanges of the trigger 46. A tension spring 48 is attached to the sliding plate 47 at a tab 52 and to a tab 53 on the trigger 46. The spring 48 biases the sliding trip plate 47 toward the trip rod 49.

The plate 47 has an aperture 51 big enough to receive the lower end of valve stem 50. But when the plate 47 is fully biased towards rod 49, aperture 51 is not aligned with stem 50 as shown in Figure 8. Thus, as the trigger 46 is lifted, the sliding plate 47 also lifts the valve stem 50. The air flow and piston action is the same as previously described in relation to Figures 1 to 7. When the piston 20 depresses the trip rod 49, an inclined surface at the end of rod 49 contacts a sloped portion 54 of the sliding plate 47.

The downward force of the trip rod 49 causes the plate 47 to slide to the left as shown in Figure 9. The movement of the plate 47 allows the end of the valve stem 50 to pass through the aperture 51 within the plate 47.

This action provides the "cycle through" operation of the tool.

Upon release of the trigger 46, a spring 56 resets the trigger to the lower position and spring 48 resets the sliding plate 47 after it has cleared the end of the valve stem 50.

Figures 11 and 1 2 show an embodiment which is a modification of that shown in Figures 1 to 7. Here the trip rod 40 is not used for accomplishing the "cycle through" action. Instead, the driving member 60 has a relieved section providing a step 61 a fixed distance from the underside of piston 20. The pawl 62 is of shape similar to that of pawl 26 except that the right-hand end is now longer in order to extend into the path of the step 61 as the driving member 60 moves downward.

The mounting of the trigger lever 27 on the adjustment block 63 by pin 31 is the same as previously described and the operational relationship between the trigger and the valve means also remain the same as previously described. As the piston 20 now bottoms out on block 63 the step 61 contacts pawl 62 causing rotation thereof and releases the valve means for retraction of the driving member 60. When the driving member 60 returns to its at rest position the pawl 62 is free to reset as the trigger lever 27 is released.

The adjustment block 63 can be vertically positioned to set the downward position of the driving member 60 with respect to the workpiece without changing the positional relationship of the piston 20, driving member 60, pawl 62 and pivot pin 31 with respect to each other. The adjustment of block 63 by turning the screw 33 is the same as previously described. The step 61 on the driving member 60 will also serve the same purpose as the trip rod 40 when the alternate valve tripping device shown in Figure 8 and Figure 9 is used. In this case the sliding plate 47 would be longer to allow the sloped portion 54 to extend into the path of the step 61 as the driving member 60 moves downward. All other functions would remain the same.

It will be apparent that, in all embodiments of fastener driving device as described herein, adjustment of the stop 32 affects the downward stroke of the piston and the driving member substantially without changing the operational relationship of the valve, the trigger and the release device (e.g. the pawl 26 or the plate 47).

Claims (10)

1. A fastener driving device comprising: a body member (15); piston means (20) mounted in said body member for reciprocating movement between a first position and a second position; drive means having an actuating member (16) and operable to drive said piston means from the second position to the first position when the actuating member is in a normal position and operable to drive said piston means from the first position to the second position when the actuating member is in an actuated position; stop means (32) which is adjustable to adjust said second position of the piston; triggering means (27) operable to move from a rest position to a triggering position thereby moving said actuating member to its actuated position; and release means (26,40; 61,62; 47,48,49) to release said actuating member to allow it to return to said normal position with the triggering means remaining in its triggering position, characterised in that said triggering means is mounted on said stop means and in that said release means (26,40; 61,62; 47,48,49) is arranged for actuation by said piston means with the piston means at a predetermined position relative to said stop means (32).

2. A device according to claim 1 characterised in that said triggering means (27) is pivotally mounted on said stop means.

3. A device according to claim 1 or 2 characterised in that said release means comprises a release element mounted on said triggering means for movement between a set position at which it engages said actuating member (1 6) when said triggering means is operated and a release position allowing said actuating member (16) to return to said normal position.

4. A device according to claim 3 characterised in that said release element is a pawl (26,62) pivotally mounted on said triggering means.

5. A device according to claim 3 characterised in that said release element is a plate member (47) slidably mounted on said triggering means.

6. A device according to any one of claims 3 to 5 characterised by release biassing means (30,48) arranged to bias said release element to said set position.

7. A device according to claim 6 characterised in that said release biassing means (30) is further arranged to bias said triggering means to said rest position.

8. A device according to any one of claims 3 to 7 characterised by a trip rod (49) mounted on said stop means (32) for engagement by said piston means to actuate said release element.

9. A device according to any one of claims 3 to 7 characterised in that an extension (60) of said piston means (20) carries an engagement element (61) for actuation of said release element.

10. A device according to any one of the preceding claims characterised by biassing means (17) arranged to bias said actuating member to said normal position.