The present invention relates to fluid operated tools in general, but more specifically to rivet squeezers operated by pneumatic power.
Pneumatic rivet squeezers are known in the art, and form an invaluable tool in the aircraft manufacturing industry. Opposing forces of some tons in magnitude can be made available to an artisan through a portable rivet squeezer. Such forces may be applied to the ends of rivets for joining structural elements together in a conventional way. The internal components of rivet squeezers have been developed over the years to provide efficiency, so that a degree of portability has been achieved in the manufacture of rivet squeezers. However, shortcoming still exist.
A basic portable rivet squeezer includes two pivoting jaws configured to provide a considerable opposing force to the external tips of the jaws. By forcing internal arms of the jaws apart, external tips of the jaws are forced together to provide the squeezing force. The force applied to open the internal arms of the jaws is typically applied by a reciprocating pneumatic ram, which is under considerable mechanical advantage through hydraulic leverage. At the tip of the pneumatic ram is a wedge which is inserted between the ends of the internal arms, forcing them apart under additional mechanical advantage. Once the squeezing force has been delivered to the rivet or other toolpiece, through the extension of the pneumatic ram, the ram is returned to its original position by a return spring system.
Although some degree of size reduction has taken place in the development of portable rivet squeezers, a current lightweight squeezer commonly may weigh around 1.7 kg. This size is an improvement on past technology, but it is still sufficiently large to present problems to artisans of small stature, such as women, who may find extended use of such a rivet squeezer to be difficult and tiring. Not only does the weight of such a device present a problem for artisans to manipulate the device with dexterity, but the size presents problems when the device is applied to smaller rivets, or rivets in awkward positions.
Thus, there is a present need for a lightweight miniaturized rivet squeezer that is capable of delivering the same squeezing force as current devices, while overcoming the shortcomings of size present in the prior art. The present invention addresses these and other needs.
According to a preferred embodiment of the invention, there is described a rivet squeezer that provides a sturdy and robust device for applying opposing forces of some tons to a rivet or other workpiece, where the rivet squeezer has the advantage of significant reduction in size, or miniaturization, over existing rivet squeezers commonly available.
In one aspect, the rivet squeezer of the present invention has a housing having a first cavity in an internal wall. A first jaw is positioned partially within the housing, the first jaw having a second cavity in an external wall. A second jaw is also positioned partially within the housing, and a wedge operable between a starting position and an ending position is provided. The wedge is adapted to be pneumatically forced from the starting position, thence between internal ends of the first and second jaws, to the ending position. In this way, the internal ends of the jaws are forced apart, and the external ends of the jaws are forced together. A return spring is provided for returning the wedge from the ending position to the starting position. The return spring is diametrically positioned partially within the first cavity in the housing, and partially within the second cavity in the first jaw. In this way, a space saving is achieved, and the diameter of the housing may be reduced in comparison with the diameter of rivet squeezers commonly available at present, in which the return spring is not accommodated, partially or at all, in a cavity in a wall of the jaw.
In a further aspect of the invention, the first jaw is, preferably, fixed to the housing, and the second jaw is pivotable about a pivot point. Further, the cavity in the first jaw is elongate and parallel to the direction of travel along which the wedge moves inside the housing of the squeezer. In this preferred aspect, the wedge is activated by a piston and the spring is positioned, at a first end of the spring, against the piston. Further, the spring may be positioned, at a second end of the spring, against a terminal point of the first cavity in the housing, and also against a terminal point of the second cavity in the first jaw.
In other aspects, a roller is pinned to the internal end of the first jaw for contacting the wedge as the wedge moves from starting to ending position. Further, a roller is pinned to the internal end of the second jaw for contacting the wedge as the wedge moves from starting to ending position.
A further feature of the invention is that the rivet squeezer may weigh less than 1 kilogram, and the length of the rivet squeezer may be less than 19 cm.
In another aspect of the invention which allows for a large force between the jaws of the rivet squeezer despite the fact that it enjoys a reduced size in comparison with presently commonly available rivet squeezers, the rivet squeezer may have a wedge that has a novel geometry capable of delivering large opposing forces despite overall miniaturization. Under this geometry, and using the terms defining the geometry of the wedge as they are defined below, the wedge may have:
In another aspect, the wedge may have a height between 1.4 inches and 1.6 inches and a width between 0.5 inches and 0.6 inches;
In yet a further preferred aspect of the invention, the rivet squeezer may include a novel method of connecting an air supply to the housing of a rivet squeezer that eliminates the need for an O-ring to form an adequate air tight seal, and which accordingly provides for further miniaturization of the squeezer. In this aspect, the rivet squeezer includes a housing, a first jaw partially included within the housing and a second jaw partially included within the housing. A wedge operable between a starting position and an ending position is provided and adapted to be pneumatically forced from the starting position, thence between internal ends of the first and second jaws, to the ending position, whereby the internal ends are forced apart, and external ends of the jaws are forced together. An internal threaded bore in the housing for receiving an air supply is provided, the threaded bore having a thread gauge and being configured to have dimensions of a U.S. standard pipe thread with a conical taper. The threaded bore ends in a cylindrical bore having a first diameter. The cylindrical bore is configured to hold a valve. An air inlet piece for supplying air to the squeezer is provided, the inlet piece having external threads configured to mate with the threads of the tapered bore, the inlet piece having a terminal end with a second diameter not greater than the first diameter. The length of the valve is such that, when the inlet piece is inserted into the bore to a standard torque, the terminal end is a distance “t” from an end of the valve, “t” being between 0.8 and 1.2 times the gauge of the bore thread. Under these circumstances, the inlet piece is torqued into the bore beyond the standard torque such that the terminal end of the inlet piece is in contact with the end of the valve, and no O-ring is used to seal the inlet piece to the bore.
Thus, without the need for an O-ring to form an adequate air tight seal under standard shop air conditions (80-120 psi), the size of the rivet squeezer in the vicinity of the air connection may be reduced, and thus the size of the rivet squeezer may be further reduced overall, to permit advantageous miniaturization and ability to manipulate the rivet squeezer with dexterity while not substantially reducing the magnitude of the squeezing force under miniaturization.
These and other advantages of the invention will become more apparent from the following detailed description thereof and the accompanying exemplary drawings.
With reference to the figures, which are provided for exemplification and not limitation, a portable rivet squeezer generally identified by the numeral 20 is described having features of the present invention. With initial reference to
The external arms 28, 30 terminate in distal ends configured to receive a rivet for squeezing. The internal arms 32, 34 terminate in rollers pinned to the arms for facilitating the application of a separating force. Specifically, the upper internal arm 32 may have a roller 42 attached by a pin 44. The lower internal arm 34 has, in a preferred embodiment, two rollers 46 attached to the lower arm by pins 48.
At the proximal end of the rivet squeezer, an air supply 50 is provided, which gains access to an internal air chamber 52 by way of a channel 54 extending through the air connector element 23. A slidable piston 56 closes off the chamber 52 so that compressed air introduced to the chamber forces the piston 56 distally under mechanical advantage in a conventional way. A ram 58 is connected to the distal end of the piston 56 for attachment of a wedge 60 that has been specially configured, according to an aspect of the present invention, to provide a novel and advantageous force profile to the jaws when the wedge is forced between the rollers 42, 46, as set forth in greater detail below. It will be appreciated that distal movement of the wedge between the rollers 42, 46 will cause the external tips of the jaws to converge under considerable mechanical advantage. The access of air to the chamber 52 is controlled by means of a valve 62 operated by a safety (dead hand) lever 64 with a spring loaded activation element 66 positioned at the distal end of the lever.
Turning to
In order to enhance the miniaturization of the device of the present invention in view of the fact that the return spring 70 may not be substantially reduced in size compared to spring sizes of known devices, the following novel features of the squeezer are provided and found to be suitable to nevertheless allow for miniaturization and for the overall operation of the squeezer. While it is known in the art to insert a return spring within a cavity of the side wall of a housing to reduce the overall diameter of such housing, it has been found that an additional novel feature of a squeezer can suitably provide for further miniaturization. Specifically, a pair of jaw slots 74 (best seen in
In a second aspect that facilitates and adds to the further miniaturization of the rivet squeezer of the present invention, the wedge 60 of the squeezer is shaped to enhance the maximum force extractable from the squeezer, to compare favorably with the maximum force presently produced by larger rivet squeezers. In this aspect, the wedge 60 is shaped according to the following geometry, which is also clarified with reference to
In yet a further aspect that facilitates the miniaturization of the rivet squeezer of the present invention, it has been determined that certain structural features described below, in addition to those described above, further provide an advantage for reducing the overall size of a rivet squeezer. It is known in the prior art to introduce air into a chamber by way of a threaded air supply inlet that is screwed into a bore of a housing and sealed against air leakage by capturing an O-ring for compression against both the housing and the air supply inlet. However, by providing an O-ring, it is required that the housing be sufficiently wide in the area local to the connection to accommodate the O-ring. An aspect of the present invention is that, by selecting a novel configuration of threading to connect the air inlet piece 76 to the air connector element 23 of the housing, this configuration eliminates the need for an O-ring to form a seal, and allows for further miniaturization (and cost reduction) of components of the squeezer 20. When incorporating these features, described in more detail below with reference to
By adopting the following structural features, it has been determined that no O-ring need be provided to achieve an adequate seal between the air inlet 76 and the air connector element 23 of the housing. Under design conditions commonly used for attaching an air inlet to a housing, the external threads of an inlet, and the internal threads of a housing, are both standard cylindrical threads, used in combination with an O-ring. Ordinarily, the inlet is screwed into a bore in the housing until it is arrested by a shoulder on the inlet or on the housing. The standard cylindrical threads provide retention of the inlet in the housing, and the O-ring provides a seal. However, with the advantage that the elimination of the O-ring provides for miniaturization, another means for providing both retention of the inlet in the housing and a seal between inlet and housing is provided by the present invention. It has been found that where a threaded system in which the external threads of the inlet, on the one hand, and the internal threads of the housing, on the other, each have a U.S. standard pipe thread geometry, this configuration will provide an adequate seal and adequate retention simultaneously—under the further condition that the mating threads are configured to permit the inlet piece to be tightened about one revolution beyond the standard torque for a standard pipe threaded connection. A standard pipe thread is not cylindrical but slightly conical, or tapered. In the ordinary course if a standard pipe thread is used, and a corresponding standard torque is applied, retention is not adequately assured because a slight outward rotation of the inlet would tend to release the inlet from the housing due to the conical configuration of the threads. Despite this, the present invention provides a novel modification on a pipe thread connection configuration that provides both adequate retention and seal.
In order to achieve the configuration as described above, there is first exemplified with reference to
Turning now to
In this way, a novel connection is formed without relying on an O-ring to form a seal, and thus a significant reduction in size of the squeezer components can be additionally achieved beyond those already described.
In yet a further aspect, arising from the miniaturization of the squeezer of the present invention described herein, it is possible to manufacture a rivet squeezer capable of delivering some tons of squeezing force between the external arms of the jaws, while at the same time making the squeezer to weigh no more than 1.0 kilograms and extend no more than 19 cm from the proximal end (excluding the air inlet piece) to the distal tips of the jaws. This is a useful weight and length reduction in light of presently available portable rivet squeezers that commonly may weigh about 1.7 kilograms and may be about 24 cm in length.
The present invention may, of course, be carried out in other specific ways than those herein set forth without departing from the essential characteristics of the invention. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.
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