Claims
- 1. A fastener driving tool having a firing valve mounted therein for selectively introducing a sufficient volume of pressurized gas into an expansible chamber for moving a piston therein to drive a fastener, and having a firing valve chamber for selective connection between the atmosphere to open the firing valve for operating the tool to drive a fastener, and a source of gas above atmospheric pressure to maintain the firing valve in closed position, the improvement comprising:
- first and second rolling seals disposed in said tool and defining between them said firing valve chamber,
- said first and second rolling seals each having a convolution disposed between said firing valve and adjacent surfaces of said tool,
- said first and second rolling seals independently supporting said firing valve for movement in said tool.
- 2. A fastener driving tool as in claim 1 wherein said firing valve comprises at least an exhaust stem and a piston, said exhaust stem and piston being separable and each defining opposed compression surface means for securing one of said rolling seals to said firing valve.
- 3. A fastener driving tool as in claim 1, wherein said firing valve includes two separable elements, one of said rolling seals having an inner portion sealingly captured between said two separable elements.
- 4. A fastener driving tool as in claim 1, wherein said firing valve includes a center post, a piston and an exhaust stem threaded onto said center post, said piston and said exhaust stem having surfaces for compressing and sealing inner portions of said rolling seals to said firing valve.
- 5. A fastener driving tool as in claim 1 wherein said first one of said seals has a convolution adjacent an inner edge of said first seal and said second seal has a convolution disposed proximate an outer edge of said second seal.
- 6. A fastener driving tool as in claim 5 wherein the convolution in said first seal is on one diameter and the convolution in said second seal is a greater diameter.
- 7. A firing valve for use in a fastener driving tool of the type having a cylinder, and a reciprocal piston therein, said firing valve for selectively sealing a cylinder from a source of pressurized air, or moving away from said cylinder to open said cylinder to pressurized air above said piston for driving it, when said firing valve is combined with a fastener driving tool, said firing valve including:
- an exhaust valve stem having an exhaust bore therein;
- a first rolling seal;
- a second rolling seal;
- a firing valve chamber defined between said seals;
- said first rolling seal sealing said firing valve chamber from said cylinder and from said exhaust bore in said exhaust stem;
- said second rolling seal sealing said firing valve chamber from atmosphere; and
- said firing valve chamber being selectively operationally connected to atmosphere or to a source of pressurized air at a pressure above that of the atmosphere for respectively firing a fastener driving tool or preventing firing of a fastener driving tool, said first and second rolling seals each having a convolution disposed between said firing valve and adjacent surfaces of said tool such that said rolling seals support and guide said firing valve for movement in said tool independently of all surfaces in said tool.
- 8. An expansible chamber apparatus disposed in a housing and including:
- A firing valve for sealing said expansible chamber from a firing valve chamber, and for selectively opening said expansible chamber to operating pressure air;
- said firing valve including reciprocable means for selectively engaging a port disposed between a pressure air source and said expansible chamber and sealing same from said pressure air source; and,
- an exhaust passage means extending through said reciprocable engaging and sealing means for selectively communicating between said expansible chamber and an area at a lower pressure than said pressure air source when said reciprocable means is in a position sealing said expansible chamber from said pressure air source;
- wherein said reciprocable engaging and sealing means includes an exhaust valve stem having a bore comprising a portion of said exhaust passage means; and
- wherein said firing valve and said firing valve chamber, are disposed in said housing;
- said apparatus further including:
- a rolling diaphragm seal operably sealing said firing valve to said housing, sealing said firing valve chamber from said exhaust passage and sealing said expansible chamber from said firing valve chamber within said housing;
- a second rolling diaphragm seal operatively sealing said firing valve chamber from said lower pressure area when said reciprocable means is moved to engage and seal said expansible chamber from said pressure air source; and
- said firing valve chamber being selectively connectable to the atmosphere or to a source of pressure greater than that of said atmosphere,
- said rolling diaphragm seals each having a convolution disposed between said firing valve and adjacent elements of said apparatus, said seals independently supporting said firing valve in said apparatus for movement therein.
- 9. A gas operated fastener driving tool comprising:
- a housing;
- an upstanding cylinder disposed within said housing and defining with said housing a housing chamber adapted to receive gas under pressure;
- a piston slidably mounted within said cylinder and provided with a fastener driver on the lower side thereof facing said lower cylinder end, said piston in response to pressurized gas supplied to the upper side of said piston being driven from a retracted position at the upper end of said cylinder to a driven position at the upper end of said cylinder to a driven position at the lower end of said cylinder;
- valve means including a firing valve and a remote trigger valve for controlling the introduction and exhaust of pressurized gas to and from the upper end of said cylinder above said piston;
- a firing valve chamber located within said housing and above said cylinder, said firing valve being reciprocable toward and away from said cylinder within said firing valve chamber to control the flow of gas under pressure from said housing chamber into the top side of said cylinder and from the top side of said cylinder to atmosphere;
- an exhaust chamber located above and sealed from said firing valve chamber;
- a pair of spaced rolling diaphragm seals, defining between them said firing valve chamber, both of said seals being connected to said firing valve and to said housing;
- said firing valve chamber being selectively connectable to the atmosphere for firing the tool or to a source of pressure above that of atmospheric to prevent firing of the tool,
- one of said seals sealing said firing valve chamber from said exhaust chamber; and
- another of said seals sealing said firing valve chamber from said housing chamber and from said exhaust chamber when said firing valve is spaced from said cylinder,
- said rolling diaphragm seals each having a convolution disposed between said firing valve and adjacent surfaces of said tool,
- said seals independently supporting said firing valve for movement in said tool.
- 10. A gas operated fastener driving tool comprising:
- a housing;
- an upstanding cylinder disposed within said housing and defining with said housing a housing chamber adapted to receive gas under pressure;
- a piston slidably mounted within said cylinder and provided with a fastener driver on the lower side thereof facing said lower cylinder end, said piston in response to pressurized gas supplied to the upper side of said piston being driven from a retracted position at the upper end of said cylinder to a driven position at the lower end of said cylinder;
- valve means including a firing valve and a remote trigger valve for controlling the introduction and exhaust of pressurized gas to and from the upper end of said cylinder above said piston;
- a firing valve chamber located within said housing and above said cylinder, said firing valve being reciprocable within said firing valve chamber from a lower position sealingly engaged with the top of said cylinder to a raised position remote from the top of said cylinder;
- an exhaust chamber located above and sealed from said firing valve chamber;
- an exhaust valve stem located within said exhaust chamber, said exhaust valve stem being attached to and reciprocable with said firing valve;
- an exhaust bore extending through said firing valve and said exhaust valve stem from the underside of said firing valve to the top side of said exhaust valve stem;
- wherein said firing valve is sealingly connected to said housing by two spaced rolling diaphragm seals, said firing valve chamber being located between said rolling diaphragm seals, being sealed from said housing chamber by one of said rolling diaphragm seals, and being selectively connectable to atmosphere or to a source of pressure above that of atmospheric,
- said rolling diaphragm seals each having a convolution disposed between said firing valve and adjacent surfaces of said tool.
- 11. The fastener driving tool of claim 10 wherein the one of said two rolling diaphragm seals sealingly separates said firing valve chamber from said housing chamber.
- 12. The fastener driving tool of claim 10 wherein said firing valve includes separable means for sealing connection to said respective seals.
Parent Case Info
This is a continuation of application Ser. No. 07/225,348, filed July 28, 1988, which in turn was a continuation of U.S. Pat. Application Ser. No. 07/130,303, filed Dec. 9, 1987 (now abandoned) which in turn was a continuation of U.S. Pat. Application Ser. No. 07/503,843 filed May 31, 1988, now U.S. Pat. No. 4,747,338.
This invention relates to pneumatic guns and more particularly to an improved firing valve for use with such guns.
Pneumatic guns for driving nails or staples are common in the commercial market. Typically, such pneumatic guns comprise a generally gun-shaped housing within which there is a cylinder containing a driving piston. This piston carries a hammer blade which is adapted to be moved past the opening of a magazine containing a roy of staples or mails to be sequentially driven by the hammer blade. As the hammer blade moves past the opening in the magazine, it engages the endmost staple or nail, causing that endmost staple or nail to be separated from the remaining staples or nails and driven into a structure. The hammer blade then is lifted or retracted, from its fired or downward position which blocks the opening of the magazine, to permit the next following nail or staple contained in the magazine to be urged forwardly into a position wherein the next fastener is directly below the hammer blade preparatory to the next stroke of the hammer blade.
Reciprocation of the piston within the cylinder of such prior art guns is commonly effected by a valve mechanism operable to supply air under pressure to the top side of the piston so as to drive it downwardly, or to the underside of the piston while the top side is connected to exhaust so as to drive the piston upwardly. The valve mechanism which controls this piston reciprocation generally comprises a trigger operated valve and a firing valve. The firing valve alternatively supplies high pressure air to the top side of the piston or connects the top side of the piston to exhaust.
One of the most important characteristics of a pneumatic gun is that the firing valve of the gun be very quick acting so as to impart maximum power to the driving piston and attached hammer blade. That power is a function of the velocity of the piston which is in turn a function of the speed with which the firing valve opens so as to deliver the maximum air flow and pressure to the piston as rapidly as possible and thereby maximize the velocity of the piston in its downward hammer stroke.
It has been one objective of this invention to provide an improved pneumatic gun firing valve which opens more quickly than prior art firing valves and therefore imparts increased velocity to the piston and attached hammer blade controlled by the firing valve.
One of the most common problems encountered by all manufacturers of pneumatic guns is that of frequency of service calls required to repair failed guns. Most of the service calls are traceable to failed seals in the gun, and quite commonly those failed seals are the seals associated with the firing valve. Upon failure of these seals, the gun ceases to operate, or alternatively delivers so little power as to effectively render the gun useless.
As presently configured, most pneumatic guns utilize either O-ring seals or diaphragm seals throughout the guns. When O-ring seals are used in pneumatic guns, though, the seals lack lubrication of the type which is usually present when such seals are utilized in hydraulic applications. Because of the absence of any lubrication, O-ring seals in pneumatic guns are generally characterized by a relatively short life. Additionally, the air systems used in association with pneumatic guns often contain contaminants which act as abrasives to further shorten the life of the O-ring seals.
The alternative to using O-ring seals in pneumatic guns has in the past been to use diaphragm seals. Diaphragm seals, though, are subject to being stretched, and since there is a limit to the amount of stretch which may be imparted to a given diameter of diaphragm seal, the diameter of the seals must be increased to obtain larger strokes of the valve. Consequently, the tops of diaphragm sealed tools are usually larger than O-ring sealed tools. And, of course, it is always desirable to minimize the size of any hand tool. Accordingly, for the most part, O-ring sealed tools have heretofore been more common than diaphragm sealed tools.
Whether the pneumatic guns use diaphragm seals or O-ring seals, they are still subject to too frequent failure of the seals and resulting breakdown of the gun. It has therefore been an objective of this invention to provide an air gun which is less subject to seal failure and to the need for repair than prior art guns.
Still another objective of this invention has been to provide an improved sealing system for the firing valve of an air or pneumatic gun which is less subject to failure and need for repair than prior art guns.
These objectives are achieved and one aspect of this invention is predicated upon the concept of utilizing rolling diaphragm seals in place of prior art O-ring seals or flat diaphragm seals in association with the firing valve of a pneumatic gun.
The pneumatic fastener driving tool of this invention which accomplishes these objectives comprises a housing having a handle and a trigger actuated valve associated with that handle. The trigger actuated valve is operative to control displacement of a firing valve. This firing valve in turn controls reciprocation of a piston within a cylinder contained within the housing. The piston has a hammer blade attached to the lower side thereof facing the bottom of the cylinder. When the trigger valve is actuated, the top side of the firing valve is vented to atmosphere through the trigger valve and thereby the firing valve is lifted upwardly by high pressure air acting upon the underside of the firing valve to move the firing valve from sealed engagement with the top surface of the cylinder. As the firing valve is lifted upwardly from sealed engagement with the cylinder, air from an air chamber contained in the housing is dumped into the top of the cylinder, thereby causing the piston and attached hammer blade to be driven downwardly. Upon release of the manual trigger, the top side of the firing valve is connected through the trigger valve to high pressure air from the housing chamber and the firing valve is thereby caused to move downwardly and seat on the cylinder, thereby connecting the top side of the piston to exhaust through the firing valve, while high pressure air entrapped beneath the piston causes the piston and attached hammer blade to return to its raised position.
The firing valve of the pneumatic gun of this invention contains top and bottom surfaces of different areas thereof and has an axial bore extending through the firing valve and through an exhaust valve stem attached to the top of the firing valve. Downward movement and sealing of the firing valve upon the top surface of the cylinder when high pressure air is supplied to the top side of the firing valve is effected by differential areas of the firing valve being exposed to the same common high pressure while simultaneously, the same high pressure acts upon the top of the exhaust valve stem. Exposure of these three different areas to the same common pressure results in the firing valve being moved downwardly and back into sealed engagement with the top of the cylinder, thereby exhausting the top side of the piston to atmosphere via the axial bore and exhaust valve stem.
One of the novel aspects of this pneumatic gun is that of having the firing valve connected to the housing by a pair of rolling diaphragm seals, which seals are connected to the top and bottom of the firing valve chamber of the housing. These seals enable the firing valve to be reciprocated within the firing valve chamber without any frictional rubbing between the seal and the valve such as occurs with conventional O-ring seals.
Still another novel aspect of this invention is predicated upon the use of a diverter attached to the underside of the firing valve and engageable with the top side of the cylinder. This diverter is of larger diameter than the top side of the cylinder and extends beyond the periphery of the top side of the cylinder. It curls downwardly so that when the top side of the firing valve is exposed to atmospheric pressure, high pressure air acting upon the underside of this diverter causes the firing valve to lift upwardly. As soon as the firing valve and attached diverter lift off of the cylinder, the diverter acts to direct air at a high velocity to the interior of the cylinder. It has been found that this downwardly curled lip on the diverter has the effect of directing air flow onto the top of the cylinder so as to increase the power and velocity of the piston.
The primary advantage of this invention is that it eliminates either O-rings or conventional flat diaphragm seals between the firing valve and the housing of a pneumatic fastener driving tool. Substitution of a rolling diaphragm seal for the conventional flat diaphragm seal or for the conventional O-ring seals has resulted in a fastener driving tool which has a longer life and which is less subject to failure than tools which incorporate either flat diaphragm seals or O-ring seals As compared to pneumatic guns which utilize flat diaphragm seals between the firing valve and the housing, the invention of this application with its rolling diaphragm seals enables the size of the head of the gun to be reduced for a given power output gun.
US Referenced Citations (21)
Foreign Referenced Citations (5)
| Number |
Date |
Country |
| 490439 |
Feb 1953 |
CAX |
| 0007534 |
Jan 1979 |
EPX |
| 0052368 |
Jun 1982 |
EPX |
| 2604287 |
Feb 1976 |
DEX |
| 0190696 |
Jan 1979 |
NZX |
Non-Patent Literature Citations (1)
| Entry |
| Advertisement for Bellofram Rolling Diaphragm in Machine Design (1983). |
Continuations (3)
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Number |
Date |
Country |
| Parent |
225348 |
Jul 1988 |
|
| Parent |
130303 |
Dec 1987 |
|
| Parent |
503843 |
May 1988 |
|
Patent Grant
4986164
