FIELD OF THE INVENTION

The embodiments described below relate to power cylinders, and more particularly, to an improved cylinder having a piston rod bumper and related method.

BACKGROUND

Power cylinders (often pneumatic or hydraulic)act to convert fluid flowing under pressure to a linear motion of a piston rod to perform a mechanical task. The most basic construction of a power cylinder comprises a tube with a rod protruding out of one of the ends. The rod has a piston attached to it, and the piston resides inside the tube. Fluid pressure acts on the piston, causing it to travel within the tube, thus causing the rod to travel into and out of the tube. A series of seals contacts the rod and the tube to prevent fluid from exiting the tube and also preventing moisture and debris from entering the tube.

Fluid flow from a control valve typically enters one oftwo ports on the cylinder. Though there are numerous ways to configure a valve with a cylinder, often one port is pressurized while the other acts as a return port. Pressurized fluid acts upon one side of the piston, which in turn forces the rod in to or out of the end of the cylinder. The direction depends on which side of the piston is pressurized by the valve. When pressure is relieved, external forces acting on the rod will cause the rod to move to the opposing position. Of course, by adjusting the valve configuration, the cylinder can be made to both extend and retract under fluid control, without the need of external forces to actuate a return stroke.

An ever-present problem in the field of fluid power cylinders is the proper cushioning or damping of the piston/rod as it completes its stroke. The main purpose of such cushioning is to prevent possible damage to the load being actuated by the cylinder and/or to the cylinder itself as could occur if the piston were to strike the end of the cylinder body at high velocity. Without proper cushioning, the piston may impact the end of the cylinder, resulting in the aforementioned damage to both the piston and the cylinder end. It is well known to damp or "cushion" the motion of a pneumatic cylinder as it approaches the end of a stroke. Usually, the cushioning comes into effect only fractionally before the end of each stroke. A multitude of structures have been employed to effectuate cushioning. One of these structures include springs of various designs placed between the piston and the end of the cylinder. The cushioning may also be provided by a bed of fluid, such as air. Also, by restricting the rate of exit of fluid from the cylinder as the piston reaches this final position, damping is created. The cushioning may also be provided by elastomeric dampening material, such as from a rubber stop, for example.

Though dampening schemes vary, they are typically configured to reside within the cylinder. However, it is known in the art to provide a bumper on the external portion of the cylinder, wherein the bumper interacts with the piston rod. As the piston rod retracts into the cylinder, the bumper retracts with the piston and simply provides a soft surface to cushion the blow of retraction.

Prior art external bumpers (FIG. 1) are held in place by securing the bumper to an end of a piston rod by threaded fasteners. In particular, a locking nut is threaded onto the end of a rod, which is typically followed by a second locking nut. The nuts act not only to hold the bumper in place, but also to act upon each other to resist unfastening. Unfortunately, cylinders are often used in high stress and high vibration environments, and the threaded locking nuts have a tendency to loosen due to vibratory stress.

There is a need for an externally bumpered cylinder that is not susceptible to vibration-induced disassembly. The embodiments described below overcome these and other problems and an advance in the art is achieved. The embodiments described below provide a power cylinder with a fixed bumper that is keyed to rod grooves and assembled with an elastic deformation fit. The result is a vibration resistant bumper that out-performs prior art units and also lowers manufacturing cost and the costs associated with maintenance.

SUMMARY OF THE INVENTION

A power cylinder with a body having a bore therein, a piston rod longitudinally reciprocable within the bore, wherein the piston rod extends axially from the body is provided according to an embodiment. According to an embodiment, a groove is defined by the piston rod, wherein the groove is disposed proximate a distal end of the piston rod, and wherein the groove circumscribes the piston rod. A bumper having a size and dimension to engage the groove engages the groove. The bumper defines an aperture having stepped diameters comprising a first inner diameter and second inner diameter, wherein the first inner diameter is approximately a diameter of the groove defined by the piston rod, and wherein the second inner diameter is approximately a diameter of the piston rod. A face disposed on a proximal portion of the bumper is configured to engage the body when the piston rod is in a substantially retracted position.

A method of manufacturing a power cylinder is provided according to an embodiment. The method comprise the step of providing a power cylinder with a body having a bore therein, a piston rod longitudinally reciprocable in the bore, and wherein the piston rod extends axially from the body. The method also comprises forming a groove in the piston rod, wherein the groove is situated proximate a distal end of the piston rod, and wherein the groove circumscribes the piston rod. A bumper is also provided. Additionally, the method comprises the step of placing the bumper in the groove of the piston rod, such that the bumper engages the body when the piston rod is in a substantially retracted position.

A fluid-powered stretch blow molding cylinder with a body having a bore therein, a piston longitudinally reciprocable within the bore, wherein the piston is connected to the piston rod, and the piston rod extends axially from the body is provided according to an embodiment. According to an embodiment, a groove defined by the piston rod is disposed proximate a distal end of the piston rod, and the groove circumscribes the piston rod. A raised distal portion with the piston rod is proximate the groove, wherein the raised distal portion of the piston rod comprises a diameter greater than the diameter of a proximate portion of the piston rod. Additionally, an annular polyurethane bumper defines an aperture, and the aperture has stepped inner diameters comprising a first inner diameter and second inner diameter, wherein the first inner diameter is approximately a diameter of the groove defined by the piston rod, and wherein the second inner diameter is approximately a diameter of the piston rod. The annular polyurethane bumper is configured to securely attach to the piston rod with an elastic deformation fit. A face is disposed on a proximal portion of the annular bumper, andface is configured to engage the body when the piston rod is in a substantially retracted position. ASPECTS

According to an aspect, a power cylinder with a body having a bore therein, a piston rod longitudinally reciprocable within the bore, and wherein the piston rod extends axially from the body, comprises a groove defined by the piston rod, wherein the groove is disposed proximate a distal end of the piston rod, and wherein the groove circumscribes the piston rod is provided. A bumper has a size and dimension to engage the groove, wherein the bumper engages the groove. The bumper defines an aperture having stepped diameters comprising a first inner diameter and second inner diameter, wherein the first inner diameter is approximately a diameter of the groove defined by the piston rod, and wherein the second inner diameter is approximately a diameter of the piston rod. A face disposed on a proximal portion of the bumper is configured to engage the body when the piston rod is in a substantially retracted position.

Preferably, the power cylinder comprises a nozzle cylinder configured for stretch blow molding.

Preferably, the power cylinder is actuated by a fluid.

Preferably, the power cylinder comprises an annular shape.

Preferably, the power cylinder further comprises a raised distal portion of the piston rod proximate the groove, wherein the raised distal portion of the piston rod comprises a diameter greater than the diameter of a proximate portion of the piston rod.

Preferably, the power cylinder is made from a compliant material.

Preferably, the complaint material is at least one of a plastic, a rubber, and a polymer.

Preferably, the complaint material is polyurethane.

Preferably, the bumper is attached to the piston rod with an elastic deformation

According to an aspect, a method of manufacturing a power cylinder comprising the steps of:providing a power cylinder with a body having a bore therein, a piston rod longitudinally reciprocable in the bore, wherein the piston rod extends axially from the body;forming a groove in the piston rod, wherein the groove is situated proximate a distal end of the piston rod, and wherein the groove circumscribes the piston rod;providing a bumper; and placing the bumper in the groove of the piston rod, such that the bumper engages the body when the piston rod is in a substantially retracted position.

Preferably, the step of providing a bumper further comprises the step ofproviding a bumper having an annular shape.

Preferably, the step of providing a bumper further comprising the step ofproviding a bumper made from a compliant material.

Preferably, the compliant material is polyurethane.

Preferably, the step of providing a bumper further comprises the step ofproviding a bumper defining an aperture, wherein the aperture has stepped diameters that comprise a first inner diameter and second inner diameter, wherein the first inner diameter is approximately a diameter of the groove defined by the piston rod, and wherein the second inner diameter is approximately a diameter of the piston rod.

Preferably, the step of placing the bumper in the groove of the piston rod further comprises:placing the first inner diameter adjacent the groove defined by the piston rod; andplacing the second inner diameter adjacent a portion of piston rod that is proximal to the groove defined by the piston rod.

Preferably, the power cylinder is actuated by a fluid.

According to an aspect, a fluid-powered stretch blow molding cylinder with a body having a bore therein, a piston longitudinally reciprocable within the bore, wherein the piston is connected to the piston rod, and the piston rod extends axially from the body is provided. The fluid-powered stretch blow molding cylinder comprises a groove defined by the piston rod, wherein the groove is disposed proximate a distal end of the piston rod, and wherein the groove circumscribes the piston rod. A raised distal portion is with the piston rod proximate the groove, wherein the raised distal portion of the piston rod comprises a diameter greater than the diameter of a proximate portion of the piston rod. An annular polyurethane bumper defines an aperture, the aperture having stepped inner diameters comprising a first inner diameter and second inner diameter, wherein the first inner diameter is approximately a diameter of the groove defined by the piston rod, and wherein the second inner diameter is approximately a diameter of the piston rod, wherein the annular polyurethane bumper is configured to securely attach to the piston rod with an elastic deformation fit. A face is disposed on a proximal portion of the annular bumper, wherein the face is configured to engage the body when the piston rod is in a substantially retracted position.

BRIEF DESCRIPTION OF THE DRAWINGS

The same reference number represents the same element on all drawings. The drawings are not necessarily to scale.

FIG. 1 illustrates a prior art power cylinder;

FIG. 2 illustrates a cross section of the prior art power cylinder of FIG. 1 ;

FIG. 3 illustrates an isometric view of an embodiment of a power cylinder;

FIG. 4 illustrates an isometric view of an embodiment of the power cylinder of

FIG. 3 in an actuated position and attached to a preform;

FIG. 5 illustrates a side view of the power cylinder of FIGS. 3-4;

FIG. 6 is a cutaway view of the power cylinder of FIGS. 3-5 being in a retracted position;

FIG.7is a cutaway view of the power cylinder of FIGS. 3-6 being in an extended position; and

FIG. 8 illustrates an embodiment of a bumper.

DETAILED DESCRIPTION OF THE INVENTION FIGS. 1-8 and the following description depict specific examples to teach those skilled in the art how to make and use the best mode of embodiments of a power cylinder and related methods. For the purpose of teaching inventive principles, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate variations from these examples that fall within the scope of the invention. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple variations of the invention. As a result, the invention is not limited to the specific examples described below, but only by the claims and their equivalents.

FIGS, land 2illustrate a prior art power cylinder 100. The power cylinder 100 illustrated is a nozzle cylinder for use in stretch blow molding applications, but any power cylinder— pneumatic, hydraulic, electric, or otherwise— is contemplated, and this example is provided for illustrative purposes, and shall not limit the invention to nozzle cylinders, as will be apparent to those skilled in the art.

A perspective view of a prior art power cylinder 100 is shown in FIG. 1. The power cylinder 100 includes a body 102 with a piston rodl04 extending therefrom. A valve block 105 attached to the body 102 aids in the control of fluid that actuates the power cylinder 100. The valve block 105 need not be attached to the body 102, and can be external to the power cylinder 100, or absent altogether in the case of an electric actuator. Across-sectional view of the power cylinder 100 is shown in FIG. 2. This view also shows the body 102 and piston rod 104, in addition to several other structures that compose the illustrative embodiment of the power cylinder 100. For example, the body 102 includes a rod borel06 and an opening 108 that receives the piston rod 104. A piston 1 10 attachable to the piston rod 104 travels longitudinally within a piston bore 1 12.

In an illustrative embodiment of the power cylinder 100 includes a piston seal 1 14 disposed about the piston 1 10 as is a guide ring 1 16. The piston 1 10 is attached to the piston rod 104so that when the piston 1 10 travels within the piston bore 1 12, the piston rod 104 travels, extending into or out from the cylinder body 102. Thus, as fluid is disposed on one side of piston 1 10 or the other, movement of the piston makes the piston rod 104 move. The piston rod 104 may be attached to a work piece (not shown). A rod seall l 8may be disposed about the periphery of the piston rod 104 proximate the opening 108 to fluidly seal the rod bore 106, keep contaminants out of the rod bore 106, and also to keep lubricating material within the body 102.

A cushionl21 proximate a rear cover 120 isdisposed at an end of the piston bore 1 12, and limits the length of retraction of the piston 1 10 (and second piston 1 1 1 that resides in a second bore 1 13) and therefore the piston rod 104. An external bumper 122 is attached to the piston rod 104. The external bumper 122 provides cushioning when the piston rod 104 retracts, thus allowing rapid retraction of the piston rod 104, while lowering the risk that the body 102, piston rod 104, pistons 1 10,, 1 1 1 or work piece (not shown)are subjected to damage due to retraction forces. The external bumper 122 is attached to the piston rod 104 by threaded fasteners 124. A single threaded fastener 124 may be used (FIG. 2) or multiple threaded fasteners (FIG. 1) may be used. In either case, the forces and/or vibrations that the power cylinder 100 are subjected to during normal operation make the threaded fasteners 124 prone to loosening. A potential result of loosening fasteners is damage to the work piece or power cylinder 100 and the related costs for production down-time and related maintenance.

Turning to FIGS. 3-7, a power cylinder 100 having an external bumper 122 is illustrated according to an embodiment. FIGS. 3-5 illustrate exterior views of a power cylinder 100. As noted above, the power cylinder 100 illustrated is a nozzle cylinder for use in stretch blow molding applications, but any power cylinder— pneumatic, hydraulic, electric, or otherwise— is contemplated, and this example is provided for illustrative purposes, and shall not limit the invention to nozzle cylinders, as would be apparent to those skilled in the art. FIGS. 6 and 7 illustrate cross-sectional views of the power cylinder 100. FIG. 4 additionally shows the power cylinder 100 attached to a SBM preform 123 for illustrative purposes.

FIG. 6 illustrates a power cylinder 100 in a retracted position. The external bumper 122 rests against the body 102 when in a retracted state. When the power cylinder 100 retracts from an extended position (see FIG. 7), the external bumper 122 lowers the forces inherent in rapid retraction of the piston rod 104, thus cushioning the piston rod 104 against the body 102.

The external bumper 122 preferably comprises a material that is softer than the material from which the body 102 is made. Preferably a compliant material is used that aids in shock absorption due to the forces associated with rapid retraction of the piston rod 104. Such materials include rubbers, plastics, thermoplastics, synthetic polymers (thermosetting polymers, thermoforming, or otherwise), and thermoplastic poly ur ethanes. Other materials known in the art are also contemplated, and as these above materials are provided as illustrative examples, theyshould not be construed as limiting the materials from which the external bumper 122 is constructed. Preferably the external bumper 122 is made from polyurethane. It is also contemplated that the external bumper be made from more than one material. For example, a relatively harder material may be coated or over-molded with a softer material.

A groove 126 is formed into the piston rod 104. This groove 126 is situated near the distal end 104a of the piston rod 104. The groove 126 is preferably cast into or more preferably machined into the piston rod 104 such that the groove substantially circumscribes the piston rod 104. This forms a continuous channel into which the bumper 122 may be installed. Although the groove 126 illustrated has a rectangular profile as an example, other shapes, such as round or undercut are also contemplated. Additionally, manufacturing processes other than casting or machining are contemplated, and will be readily appreciated by one skilled in the art.

In one embodiment of a groove 126, a first surface 128 extends inwards from the diameter of the piston rod 104 to a diameter 130 that defines the depth of the groove 126. In the embodiment illustrated, a protrusion 132 (raised distal portion) extends from the piston rod 104. The protrusion 132 helps to prevent the bumper 122 from disengaging from the piston rod 104. The protrusion 132 may have a protrusion diameter 134 that is the same as the piston rod's diameter. In a preferred embodiment, the protrusion diameter 134 is greater than the piston rod's diameter. A second surface 136 extends inwards from the protrusion diameter 134 to the diameter 130 that defines the depth of the groove 126. As is clear by FIGS. 6 and 7, the bumper 122 is maintained in the groove 126 and travels away from and towards the body 102 with the piston rod 104 as the piston rod 104 is extended and retracted, respectively.

With additional reference to FIG. 8, the bumper 122 has a size and dimension to engage the groove 126 so that when installed on the piston rod 104,a face 136 of the bumper 122 may contact the body 102 when the piston rod 104 is in a substantially retracted position. In a preferred embodiment, the bumper 122 is an annular shape. Other shapes, however, are contemplated. The bumper 122 defines an aperturel38 or opening that passes substantially through the bumper 122. The aperture 138has stepped diameters. A first inner diameter 140 is approximately a diameter 130 of the groove defined by the piston rod 104. The second inner diameter 142 is approximately thediameter of the piston rod 104.

To install the bumper 122, the piston rod 104 is placed through the aperture 138 until the first inner diameter 140 mates to the diameter 130 of the groove 126 and the second inner diameter 142 mates to the outer diameter of the piston rod 104. An outer face 144 of the bumper 122 engages a second surface 146 that is defined by an inner surface of the protrusion 132. In an embodiment, the first inner diameter 140 and second inner diameter 142 are slightly smaller than the diameters 104b, 104c of the piston rod 104 to which they respectively mate. This provides a tight deformation fit when the bumper 122 is installed on the piston rod 104. In another embodiment, the first inner diameter 140 is slightly smaller than the diameter 104b of the piston rod 104 to which it mates, while the second inner diameter 142 is slightly larger than the diameter 104c of the piston rod 104 to which it mates to promote easier assembly. The tight deformation fit is just one advance over prior art threaded fasteners, as this attachment means is resistant to loosening due to vibration and other forces that are customary during cylinder use. Additionally, a larger protrusion diameter 134 (relative to the piston rod 104 diameter) provides additional bearing surface area that traps the bumper 122 in place, thus preventing its inadvertent disengagement from the piston rod 104.

An embodiment also contemplates a method of manufacturing a fluid-powered cylinder 100. The method comprises a number of steps, including providing a fluid- powered cylinder 100 with a body 102 having a bore 106 therein and also a piston 1 1 1 that is longitudinally reciprocable in a second bore 1 13. A piston rod 104 extends axially from the body 102. A groove 126 is placed in the piston rod 104, by casting, machining, or other manufacturing processes known in the art. As discussed above, the groove is preferably situated proximate a distal end 104a of the piston rod 104. The groove 126 circumscribes the piston rod 104. A bumper 122 is provided and placed in the groove 126 of the piston rod 104, such that the bumper 122 engages the body 102 when the piston rod 104 is in a substantially retracted position. The bumper 122 provided may have an annular shape, and in a related embodiment is made from a compliant material, but other shapes are contemplated, and will be readily known to one skilled in the art.

Another step of a method of manufacturing a fluid-powered cylinder 100 comprises providing a bumper 122 that defines an aperture 138, wherein the aperture 138 has stepped diameters 140, 142 that comprise a first inner diameter 140 and a second inner diameter 142, wherein the first inner diameter 140 is approximately a diameter of the groove 126 defined by the piston rod 104, and wherein the second inner diameter 142 is approximately a diameter of the piston rod 104. The method of manufacturing a fluid- powered cylinder 100 also may further include installing the bumper 122 on the piston rod 104 by placing the first inner diameter 140 adjacent the groove 126 defined by the piston rod 104, andplacing the second inner diameter 142 adjacent a portion of piston rod 104 that is proximal to the groove 126. The detailed descriptions of the above embodiments are not exhaustive descriptions of all embodiments contemplated by the inventors to be within the scope of the invention. Indeed, persons skilled in the art will recognize that certain elements of the above-described embodiments may variously be combined or eliminated to create further embodiments, and such further embodiments fall within the scope and teachings of the invention. It will also be apparent to those of ordinary skill in the art that the above-described embodiments may be combined in whole or in part to create additional embodiments within the scope and teachings of the invention.

Thus, although specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. The teachings provided herein can be applied to other devices and method, and not just to the embodiments described above and shown in the accompanying figures. Accordingly, the scope of the invention should be determined from the following claims.