Piston Diaphragm Assembly

BACKGROUND OF THE INVENTION

The present system relates to a piston-diaphragm assembly for use in a fill pump of a container filling machine. One such machine is disclosed in U.S.S.N. 08/315,246, filed September 29, 1994, entitled "Packaging Machine System For

Filling Primary And Secondary Products Into A Container," which is hereby incorporated by reference.

Prior piston-diaphragm assemblies have utilized diaphragm that are mounted to the piston using an adhesive mount. One such prior assembly is illustrated in Figure 1. As illustrated, a flexible diaphragm 10, is mounted to a plate 15 using an adhesive at the interface therebetween. The plate 15 comprises a circular member having a threaded extension 20. The threaded extension 20 engages a corresponding threaded portion of a piston 25. Piston 25 includes a recessed portion 30 for accepting plate 15 when plate 15 is screwed to the piston 25.

A further flexible diaphragm 35 is disposed on an opposite end of the piston 25. The further diaphragm 35 includes a cut-out portion through which end 40 of piston 25 protrudes. The remaining flange 45 of the further diaphragm 35 is secured against the piston 25 by a holder 46, washer 50, and securement screws (not illustrated in Figure 1) that extend through the holder 46 and washer

50 to engage the piston 25.

In operation, the holder 46 engages a drive rod that is used to mechanically move the piston 25 in the directions illustrated by arrow 55. End portion 60 of diaphragm 10 is fixedly secured, for example, over a pump opening that is in fluid communication with a fluid source and fluid exit.

As the piston 25 is driven in the directions of arrows 55, it is alternately compressed and expanded to expel and suction fluid, respectively. Such compression and expansion creates stress on the adhesive bond between the diaphragm 10 and plate 15. Over time, the adhesive bond fails and the diaphragm 10 and plate 15 must be either repaired or replaced. Such failures increase the cost of running the machine and, further, result in costly down time during which the machine is not producing.

BRIEF SUMMARY OF THE INVENTION An improved piston diaphragm assembly is provided. The assembly comprises a piston having a first end and a second end. A center hole is located in the first end of the piston. In addition, a channel is formed in the first end of the piston. The piston diaphragm assembly further comprises a diaphragm having a rib portion. A plate is constructed and arranged to capture the rib portion of the diaphragm in the channel of the piston. The plate is secured by connecting means for holding the plate to the piston. The connecting means passes through the plate and mounts to the center hole of the piston.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

Figure 1 is a side, cross-sectional view of a prior piston-diaphragm assembly.

Figure 2 is a side, cross-sectional view of one embodiment of an improved piston-diaphragm assembly.

Figure 3 is an exploded view assembly diagram for the piston-diaphragm assembly of Figure 2, including a corresponding drive rod assembly and guide rod assembly.

Figure 4 is a perspective view of the assembled piston-diaphragm assembly of Figure 3.

DETAILED DESCRIPTION OF THE INVENTION

An improved piston-diaphragm assembly is shown generally at 100 of

Figure 2. The piston-diaphragm assembly 100 includes first and second diaphragms 105, 110 disposed at opposite ends of a piston 1 15. The first and second diaphragms 105, 110 may be similarly or identically constructed and include rib portions 120, 125, respectively.

The rib portion 120 of the first diaphragm 105 engages a circular channel 130 disposed in end portion 135 of the piston 115. A diaphragm plate 140 is placed into the interior portion of the first diaphragm 105 and is secured with a centrally disposed screw 145 that extends through a central aperture 147 in the diaphragm plate 140 to engage a corresponding threaded aperture 150 in the piston 115. An O-ring 155 may be used to seal the area between the screw 145 and the central aperture 147. The diaphragm plate 140 includes a flanged portion 160 disposed about its outer perimeter that urges the rib portion 120 into the circular channel 130.

The rib portion 125 of the second diaphragm 110 engages a circular channel 165 disposed in end portion 170 of piston 115. A washer 175 is disposed about a protruding portion 180 of the piston 115. A diaphragm holder 185 is disposed over the washer 175. Securements, such as screws, extend through a flanged portion 190 of holder 185 and the washer 175 and into the piston 115 to thereby secure the second diaphragm 110.

The channels 130, 165 and rib portions 120, 125 are dimensioned so that the rib portions 120, 125 are compressed within the channels 130, 165 when the diaphragms 105, 110 are secured to the respective ends of the piston. In this manner, a liquid seal is provided between the diaphragms 105, 110 and the piston

1 15.

An exploded view assembly drawing illustrating the foregoing diaphragm- piston assembly 100 and a corresponding drive rod assembly 200 and guide rod assembly 205 are shown in Figure 3. A perspective view of the assembly of Figure 3 is illustrated in Figure 4.

While particular elements, embodiments and applications of the present invention have been shown and described, it will be understood, of course, that the invention is not limited thereto since modifications may be made by those skilled in the art, particularly in light of the foregoing teachings. It is therefore contemplated by the appended claims to cover such modifications as incorporate those features which come within the spirit and scope of the invention.