Stud driver and spring therefor

Details Stud driver and spring therefor Stud driver and spring therefor

1998-04-16

2001-02-06

Vo, Peter (Department: 3721)

Elongated-member-driving apparatus

Explosive-type driving means

With plunger

C173S162100, C173S211000

Reexamination Certificate

active

06182881

ABSTRACT:

TECHNICAL FIELD AND BACKGROUND OF THE INVENTION
The invention relates to a stud gun or stud driver by means of which fasteners, as a rule in the form of a nail or stud, can be driven into place. The stud driver contains a propelling piston driven by the propellant gas discharge on ignition of the cartridge, the forward movement of the piston driving the stud into place.
It is particularly in the case of automated operation of such a stud driver in which the fasteners to be driven into place are supplied by means of a crib incorporated in the driver that it is desirable to automatically return the propelling piston to its starting position.
A stud driver of this kind is already known (U.S. Pat. No. 3,331,546) in which for this purpose a plurality of disk springs is arranged about a piston rod of a propelling piston. These disk springs are preferably made of polyurethane and arranged alternatively reversed so that a pack of disk springs materializes, each of which is not connected to the other.
SUMMARY OF THE INVENTION
The invention is based on the object of defining a stud driver in which the propelling piston is returned after driving the fastener and in which the driver features a long useful life without the spring needing to be changed. The invention is also based on the object of defining a spring for such a stud driver.
To achieve this object the invention proposes a stud driver comprising a housing, a propelling piston arranged reciprocatingly in the housing, the propelling piston being propellable by a propellant and configured for driving a fastener into place, and including a spring of an elastic deformable material, more particularly an elastomeric material for returning the propelling piston to its starting position after driving action; the invention also proposing a spring comprising one or more of the features as set forth in the claims relating to the spring. Further aspects of the invention read from the sub-claims.
By arranging a spring which is tensioned against its spring force on driving the fastener in place it is now possible in a simple configuration of the driver for the propelling piston to be returned to its starting position after driving, i.e. a new fastener can be inserted directly after driving.
In another aspect of the invention it may be provided for that the propelling piston comprises a piston rod of reduced diameter which is surrounded over at least part of its length by a sleeve-shaped spring.
In assembling the driver the spring proposed by the invention is simply placed over the piston rod and the driver then assembled, i.e. there is now no need to take care to ensure that the individual disk springs are inserted alternatively reversed.
In yet another aspect of the invention it may be provided for that the spring extends between a driver part not involved in the movement of the propelling piston and the propelling piston, i.e. the spring directly engages the propelling piston.
Especially in still a further aspect of the invention it may be provided for that the spring engages a braking element acting together with the propelling piston, this meaning that towards the end of the driving movement of the propelling piston, i.e. when the spring is tensioned stronger, this movement is translated partly into a braking movement by the braking element.
The spring configured in this way may be, for example, a tension spring, it being, however, particularly of advantage when the spring is configured as a compression spring so that it is subject to pressure when driving the fastener into place.
In accordance with the invention a further aspect may provide for the spring comprising stiffening elements distributed over its length which themselves do not deform. The stiffening elements may be made partly of a harder and/or other material, as a result of which the deformation of the spring is confined to small portions between two reinforcing elements each so that the deviation of the spring from being roughly cylindrical also when subject to compression can be maintained small.
It is especially in yet a further aspect of the invention that it may be provided for that during the movement of the propelling piston the stiffening elements are guided by the latter and/or by the the travel of the piston, i.e. preventing the spring made of an elastomeric material from being deformed one-sidedly during the high-speed driving movement or becoming so twisted that the driving movement of the piston is obstructed or is even ruined thereby.
It may be especially provided for that the stiffening elements are metallic ring disks, the outer diameter of which roughly corresponds to the inner diameter of the piston travel so that they are guided at their outer side. Furthermore, their inner diameter may roughly correspond to the outer diameter of the piston rod so that they are also guided at their inner side, thus being preventing them from being tilted.
In accordance with the invention it may be provided for that the spring is vulcanized together with the reinforcing elements, as a result of which an integral spring materializes which can be produced as a single element featuring all desired properties.
In particular it may be provided for that the spring has a wall thickness which is maximally half as much, preferably maximally a third as much as the difference between the radius of the reinforcing elements and the radius of the internal opening in the reinforcing elements. As a result of this it is ensured that the spring in the compressed condition features a relatively small axial length, dictated substantially only by the thickness of all reinforcing elements thereby firmly in contact with each other to form a block.
In this arrangement the sleeve-like spring is arranged to advantage in the vicinity of the internal opening of the reinforcing elements and thus in the vicinity of the piston rod. Accordingly, its deformation is primarily radially outwards.
In the non-deformed condition the spring is preferably cylindrical in shape.
More particularly, the reinforcing elements may be arranged equidistant, this resulting, among other things, in there being no front and rear end of the spring, i.e. orientation of the spring now being uncritical in assembling the driver.
The reinforcing elements may be arranged to advantage so that their mutual spacing corresponds to roughly half their diameter.


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German search report in Appln. No. 196 38 341.2, dated Jan. 29, 1997.
European search report in Appln. No. 97115895.1-2306, dated Dec. 11, 1997.

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