US 5,927,561 AGrant
Reciprocating Liquid Pump With Disc Check Valve for Dispensing Lotion and the Like
Issue Date:1999-07-27
•18 Claims
•3 Drawing Sheets
Abstract
A manually operated pump comprises a pump housing and a plunger. The pump housing has a pump chamber and an intake port. The plunger extends into the pump chamber. A piston is on the plunger and is reciprocally and axially slidable within the pump chamber between a bottom stroke position and a top stroke position. The fluid pump further includes a priming valve, a check valve, a sealing plug, and a plug seat. The priming valve permits fluid to flow upward through the pump chamber when the piston stroke moves the piston downward from the top stroke position toward the bottom stroke position, and prevents fluid from flowing upward through the pump chamber when the piston stroke moves the piston upward from the bottom stroke position toward the top stroke position. The check valve has a valve seat and a moveable valve member moveable between a closed position in which the moveable valve member moveable between seated and unseated positions. The plug seat is downstream of the check valve and upstream of the priming valve. The sealing plug is configured to seat against the plug seat and seal closed the intake fluid flow path when the piston is in its bottom stroke position to prevent fluid from flowing upward through the intake fluid flow path. The moveable valve member of the check valve and one of the sealing plug and plug seat are of a single unitary piece.
Metadata
Assignee
- Continental Sprayers International, Inc.
Inventors
- Donald D. Foster
- Philip L. Nelson
Application Information
Application Number:US 1354922
Filing Date:1998-08-17
Priority Date:1996-05-07
Art Unit:372
Classifications
IPC:
B67D 540
Field of Search:
222153.13;321.2;321.7;321.8;321.9;341;385;494
Patent Drawings (3 sheets)
Description
Background of the Invention
This invention relates to a manually operated reciprocating fluid pump for dispensing lotions and other liquids.
A conventional reciprocating liquid pump for a lotion-type dispenser typically includes a plunger with a dispensing head that is manually reciprocated downwardly into a pump housing connected to a liquid container, a spring for biasing the plunger upwardly out of the pump housing, a priming valve, and a check valve. The priming valve unseats (opens) on the downward movement of the plunger into the pump housing to allow air in the empty pump housing to escape through the plunger and dispensing head, and then seats (closes) on the return stroke of the plunger upwardly out of the pump housing to draw liquid in the container up into the pump housing. The check valve seats on the downward movement of the plunger to prevent air or any liquid contained in the pump housing from being forced back into the container, and then unseats on the upward movement of the plunger to allow the vacuum created in the pump housing by the plunger's upward movement to draw liquid from the container past the check valve into the pump housing.
Often, ball valves are used for both the priming valve and check valve in manually reciprocated liquid pumps. However, ball valves typically require inwardly directed protrusions or some other type of stop to prevent the ball from traveling too far away from the valve seat. Such protrusions and stops are difficult to mold and increase the cost of manufacture. Also, when gritty product is the fluid to be dispensed, it often prevents a ball valve from seating properly against the valve seat, thereby reducing the effectiveness of the dispenser. Another disadvantage of ball valves is that the functioning of ball valves is dependent on gravitational forces which direct the ball of the valve downwardly to its seated position. If a liquid container having a reciprocating pump with ball valves is moved from its upright orientation, e.g., if it is placed on its side or inverted during shipment, gravity no longer seats the ball valves and the liquid in the container can pass through and leak from the pump.
Summary of the Invention
Among the several objects of the present invention may be noted the provision of an improved liquid dispenser; the provision of such a dispenser which avoids the use of ball valves; the provision of such a dispenser which effectively dispenses a wide variety of liquid products including gritty products; the provision of such a dispenser having a priming valve and a check valve which are operable regardless of whether the dispenser is placed upright, inverted, or on its side; the provision of such a dispenser configured to prevent leakage when the dispenser is inverted or placed on its side; and the provision of such a dispenser which is of relatively simple construction and which is relatively inexpensive to manufacture.
In general, a manually operated reciprocating fluid pump of the present invention comprises a pump housing and a plunger. The pump housing has an inner surface, an intake port, and a pump chamber defined at least in part by the inner surface. An intake fluid flow path is defined at least in part by the pump housing and provides fluid communication between the intake port and the pump chamber. The plunger is configured for extending axially downwardly into the pump chamber. A piston is on the plunger and is slidable within the pump chamber. It is configured for being in sealing engagement with the inner surface of the pump housing all around the piston to seal against leakage of fluid between the inner surface of the pump housing and the piston. The piston is reciprocally and axially slidable within the pump chamber between a bottom stroke position and a top stroke position. The top stroke position is spaced axially above the bottom stroke position.
The fluid pump further includes a priming valve, a check valve, a sealing plug, and a plug seat. The priming valve is configured to be open and thereby permit fluid to flow upward through the pump chamber when the piston stroke moves the piston downward from the top stroke position toward the bottom stroke position. It is further configured to be closed and thereby prevent fluid from flowing upward through the pump chamber when the piston stroke moves the piston upward from the bottom stroke position toward the top stroke position. The check valve is in the intake fluid flow path and has a valve seat and a moveable valve member moveable between a closed position in which the moveable valve member seats against the valve seat to seal against fluid leakage from the pump chamber to the intake port and an open position in which at least part of the moveable valve member is spaced away from the valve seat to permit fluid to flow from the intake port to the pump chamber. The plug seat is within the intake fluid flow path. The sealing plug is configured to seat against the plug seat and seal closed the intake fluid flow path when the piston is in its bottom stroke position to prevent fluid from flowing upward through the intake fluid flow path. The sealing plug is configured to be unseated from the plug seat when the piston is positioned above its bottom stroke position. The moveable valve member of the check valve together with one of the sealing plug and plug seat are of a single unitary piece.
Other objects and features will be in part apparent and in part pointed out hereinafter.
Brief Description of the Drawings
FIG. 1 is a side elevational view, in section, of a lotion dispenser of the present invention showing a piston of the dispenser in a bottom stroke position;
FIG. 2 is a side elevational view, in section, of the lotion dispenser of FIG. 1 showing the piston in a top stroke position;
FIG. 3 is a side elevational view of a seal member of the lotion dispenser of FIGS. 1 and 2, the seal member having a generally tubular portion defining a plug seat and a flexible disc-shaped flap constituting a moveable valve member of a check valve;
FIG. 4 is a side elevational view, in section, of the seal member of FIG. 3;
FIG. 5 is a bottom plan view of the seal member of FIG. 3;
FIG. 6 is a top plan view of the seal member of FIG. 3; and
FIG. 7 is an enlarged fragmented side elevational view, in section, of the lotion dispenser of FIG. 1 showing the seal member of FIG. 3 within a pump housing of the lotion dispenser.
Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.
Description of the Preferred Embodiment
Referring now to the drawings, a lotion dispenser of the present invention is indicated in its entirety by the reference numeral 20. Although characterized as a lotion dispenser, it is to be understood that other liquids may be dispensed via the lotion dispenser 20 without departing from the scope of this invention. The lotion dispenser 20 comprises a pump housing, generally indicated at 22, a plunger, generally indicated at 24, and a lotion dispensing head, generally indicated at 26.
The pump housing 22 has a tubular, cylindrical configuration 28 with a generally cylindrical interior surface 30. A ring 32 is formed at the top of the pump housing 22 and is configured for seating on the top edge of a liquid bottle (not shown). A threaded collar (or cap) 34 is mounted on the pump housing 22 for rotation about a central axis X of the housing. The threaded collar 34 receives a threaded neck (not shown) of the bottle. A pair of vent openings 36 extend through the pump housing 22 just below the ring 32 to vent the bottle interior through the housing interior. The cylindrical interior surface 30 of the pump housing 22 defines, in part, a pump chamber 38 for receiving the plunger 24.
Referring now to FIGS. 3-7, a monolithic (unitary) one-piece seal member, generally indicated at 40, is within a lower end of the pump chamber 38. The pump housing 22 further includes a lower tubular portion 41 below the pump chamber 38. The seal member 40 includes a base portion 42 sized and configured for being press-fit or otherwise secured in an upper end of the lower tubular portion 41, an upstanding tubular projection 43 extending upward from the base portion into the pump chamber 38, a protrusion 44 extending downwardly from the base portion, and a thin, generally disc-shaped flap 46 extending radially outwardly from the protrusion. The base portion has a circular shoulder 110 that extends radially outwardly from the base portion. The base shoulder has a bottom surface 112 that engages a ledge 114 of the pump housing that projects radially inwardly from the pump housing interior surface 30 into the liquid flow path. The base shoulder also has a top surface 116. The spring 90 engages the base shoulder top surface 116 and holds the base in its press fit axial position relative to the pump housing. The disc-shaped flap 46 is engageable with an annular shoulder 47 (FIG. 7) of the lower tubular portion 41 of the pump housing 22. Preferably, the seal member 40 is of a suitable elastomeric material, such as low density polyethylene (LDPE), so that the thin disc-shaped flap 46 is flexible.
The disc-shaped flap 46 and the annular shoulder 47 constitute a check-valve, generally indicated at 48. In particular, the disc-shaped flap 46 constitutes a moveable check-valve member (also indicated by reference number 46) of the check-valve 48, and the annular shoulder 47 constitutes a check-valve seat 47. The annular check-valve seat 47 defines an intake port 50 of the pump housing 22 adapted for fluid communication with a source of fluid (e.g., liquid in the bottle). An intake fluid flow path through liquid channels 118 the seal member 40 provides fluid communication between the intake port 50 and the pump chamber 38. The disc-shaped check-valve member 46 is moveable between a closed (or seated) position and an open (or unseated) position. In the closed position (shown in solid in FIG. 7), the flexible check valve member sealingly engages the check-valve seat 47 all around the check-valve seat to block fluid communication between the pump chamber 38 and the intake port 50. In the open position (shown in phantom in FIG. 7), at least a part of the moveable check-valve member 46 resiliently flexes upwardly away from the check-valve seat 47 to thereby provide a gap between the moveable check-valve member and the check-valve seat for fluid communication between the intake port and the pump chamber 38. Because of the shape and flexibility of the check-valve member 46, the check-valve member desirably moves between its open and closed positions even when a gritty liquid is being dispensed.
A dip tube 54 is secured to the bottom end of the lower tubular portion 41 of the pump housing 22 and is preferably configured for extending downwardly to the bottom of the bottle.
The plunger 24 is configured for extending axially downwardly into the pump chamber 38 of the pump housing 22 and has a cylindrical, tubular configuration 56 with a cylindrical interior passageway 58 therein. A downwardly extending protrusion 60 is located generally at a bottom portion of the plunger 24 and under the cylindrical interior passageway 58 of the plunger. Preferably, the protrusion 60 is generally circular in transverse cross-section (i.e., as viewed in a cross-section taken along a plane perpendicular to the axis X) and has a generally hemispherical lower end. The protrusion 60 includes lateral slits 62 therethrough for passage of liquid through the slits and into the interior passageway 58 of the plunger 24. The lateral slits 62 and the interior passageway 58 of the plunger 24 constitute a discharge fluid passageway 64 of the plunger. The lotion dispensing head 26 is secured to the top end of the plunger 24. It includes a discharge port 66 and a passageway 68 through the dispensing head 26 in fluid communication with the discharge fluid passageway 64 of the plunger 24. Because of this, liquid flowing upwardly through the plunger can flow through and be dispensed from the lotion dispensing head 26 via the discharge port 66. Although the dispenser 20 preferably has a lotion dispensing head, other heads may be employed without departing from the scope of this invention. For example, the lotion dispensing head 26 may be replaced by a spray head specifically designed to dispense liquid from the head in a spray pattern. The spray head would likely be preferred when the pump of the invention is employed in dispensing a less viscous fluid from the container.
Preferably, the dispensing head 26 has a locking tab 72 projecting laterally from one side of the head. The locking tab 72 engages beneath an annular flange 74 (FIG. 1) of a locking ring 76 secured to the upper end of the pump housing 22. The flange 74 of the locking ring 76 has an opening 78 at one position on its circumference that allows the locking tab 72 to pass therethrough. By rotating the lotion dispensing head 26 relative to the threaded cap 34 so that the locking tab 72 is aligned with the opening 78, the dispensing head and plunger 24 are free to reciprocate through a stroke movement of the plunger relative to the pump housing 22. By depressing the plunger 24 downwardly through the locking ring 78 and threaded cap 34 so that the locking tab 72 passes through the locking ring opening 78, and then by rotating the lotion dispensing head 26 so that the locking tab does not align with the opening, the plunger 24 is locked in its relative position to the pump housing 22. A sealing ring 80 is also provided between the exterior of the plunger 24 and the interior of the locking ring 76 for providing a fluid-tight seal between the interior surface 30 of the pump housing 22 and the bottle exterior.
A piston 82 is formed on the exterior of the plunger 24 and circumscribes the downwardly extending protrusion 60. The piston 82 is slidable within the pump chamber 38 and is configured for sealing engagement with the inner surface of the pump housing 22 all around the piston to seal against leakage of fluid between the inner surface of the pump housing and the piston. The piston 82 is reciprocally slidable within the pump chamber 38 along the axis X between a bottom stroke position (FIG. 1) and a top stroke position (FIG. 2). The piston 82 and pump chamber 38 define a variable volume fluid receiving cavity 84. The fluid receiving cavity 84 has a first volume V.sub.1 when the piston 82 is in its top stroke position (FIG. 2) and has a second volume V.sub.2 smaller than the first volume V.sub.1 when the piston is in its bottom stroke position (FIG. 1). The discharge fluid passageway 64 of the plunger 24 and dispensing head 26 constitute a discharge fluid flow path for providing fluid communication between the fluid receiving cavity 84 and the discharge port. The plunger 24 has an annular shoulder 88 formed on its exterior surface that engages against the underside of the sealing ring 80 to limit upward movement of the plunger 24. A coil spring 90 is positioned between the bottom of the plunger 24 and the bottom of the pump chamber 38 of the pump housing 22. The spring 90 extends around the upstanding tubular projection 43 of the seal member 40 and engages the base portion 42. The spring 90 biases the plunger 24 upwardly to its top stroke position relative to the pump housing and further maintains the position of the seal member 40 relative to the pump housing.
A priming valve 92 is mounted on the plunger 24 adjacent the protrusion 60 of the plunger and radially inwardly of the piston 82 for movement with the plunger. The protrusion 60 is shaped and configured for acting as a valve seat for the priming valve 92. The priming valve 92 has a resilient tubular portion 94 engageable with the protrusion 60, and an annular sealing flange 96 just below and circumscribing the tubular portion. The sealing flange 96 is configured for sealing against an annular shoulder 98 defined by the inner surface of the plunger 24 all around the sealing flange to prevent leakage of fluid therebetween. Because the priming valve 92 moves with the plunger 24, the sealing flange 96 remains sealed to the annular shoulder 98 of the plunger regardless of whether the priming valve is open or closed. Preferably, the upper end of the coil spring 90 presses upwardly against the annular sealing flange 96 to bias it in sealing engagement with the annular shoulder 98. The priming valve 92 further includes a sealing plug 100 (described in greater detail below) and lateral openings 102 through the sealing plug providing a fluid passage through the priming valve. The priming valve 92 is moveable between a closed position and an open position. In the closed position, the resilient tubular portion sealingly engages the protrusion 60 all around the tubular portion to block fluid communication between the discharge fluid passageway 64 of the plunger 24 and the fluid receiving cavity 84. In the open position, at least a part of the tubular portion 94 flexes generally radially outwardly away from the protrusion 60 to thereby provide a gap between the tubular portion and protrusion for fluid communication between the fluid receiving cavity 84 and the discharge fluid passageway 64 of the plunger 24.
The sealing plug 100 and priming valve 92 are of a single unitary piece and preferably formed of an elastomeric material. The sealing plug 100 is configured to seat against and seal closed the upstanding tubular projection 43 of the seal member 40 when the piston 82 is in its bottom stroke position to prevent fluid from flowing upward through the pump chamber 38. Thus, the upper end of the tubular projection 43 constitutes a plug seat. When the piston 82 is positioned above its bottom stroke position, the sealing plug 100 is spaced above the upstanding tubular projection 43 of the pump housing 22 and is therefore unseated therefrom.
The liquid pumping and dispensing operation of the lotion dispenser 20 is similar to that of conventional reciprocating pumps. Manually depressing the lotion dispensing head 26 downwardly causes the plunger 24 and piston 82 to move downwardly to the bottom stroke position. This downward movement causes the resilient tubular portion 94 of the priming valve 92 to flex radially outwardly to open the priming valve and thereby permit fluid, whether air when initially priming the pump or the container liquid after the pump has been primed, to pass from the pump chamber 38 through the priming valve through the lateral slits 62 of the protrusion 60 into the discharge fluid passageway 64 of the plunger 24 and out the discharge port 66 of the lotion dispensing head. Releasing the manual force on the lotion dispensing head 26 allows the coil spring 90 to push the plunger 24 and piston 82 upwardly to the top stroke position. This upward movement creates a vacuum in the fluid receiving cavity 84 which unseats the moveable check-valve member 46 and draws liquid up the dip tube 54 through the seal member 40 and into the fluid receiving cavity 84. This vacuum also forces the resilient tubular portion 94 of the priming valve 92 radially inwardly to close the priming valve. By continued reciprocating movement of the plunger 24 relative to the pump housing 22, the liquid is continued to be drawn from the container and dispensed through the dispensing head 26.
When the plunger 24 and piston 82 are in their bottom stroke positions and when the dispensing head 26 is locked to the collar 34 as shown in FIG. 1, the plug 100 seats against the upstanding tubular projection 43 of the seal member 40 to block flow of fluid through the dispenser 20. In this position, liquid will not leak from the dispenser 20 even if the dispenser is tilted or inverted. Because the seal member 40 includes both the plug seat and the moveable check valve member 46, the other components of the dispenser 20 are of simpler shapes which reduce the cost of manufacture of these other components.
Although the seal member 40 preferably includes both a plug seat and a moveable check valve member, it is to be understood that other constructions are possible without departing from the scope of this invention: For example, instead of having the plug seat 43 on the seal member 40 which receives a sealing plug 100 of the priming valve 92, the seal member could have a sealing plug which engages a plug seat formed with the priming valve. With such a modified dispenser, it is to be understood that the sealing plug would include lateral openings similar to the lateral openings 102 associated with sealing plug 100.
In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.
As various changes could be made in the above construction without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. The invention therefore shall be limited solely by the scope of the claims set forth below.
Claims
What is claimed is:
1. A manually operated reciprocating fluid pump comprising: a pump housing having an interior surface, an intake port, and a pump chamber defined at least in part by the interior surface, said pump chamber extending axially within the pump housing; an intake fluid flow path defined at least in part by the pump housing, said intake fluid flow path providing fluid communication between the intake port and the pump chamber; a plunger configured for extending axially downwardly into the pump chamber; a piston on the plunger and in the pump chamber, the piston being configured for sealing engagement with the interior surface of the pump housing to seal against leakage of fluid between the interior surface of the pump housing and the piston, the piston being reciprocally and axially slidable within the pump chamber between a bottom stroke position and a top stroke position, the top stroke position being spaced axially above the bottom stroke position; a priming valve configured to be open and thereby permit fluid to flow upward through the pump chamber when the piston stroke moves the piston downward from the top stroke position toward the bottom stroke position, the priming valve further being configured to be closed and thereby prevent fluid from flowing upward through the pump chamber when the piston stroke moves the piston upward from the bottom stroke position toward the top stroke position; a check valve in the intake fluid flow path having a valve seat and a moveable valve member moveable between a closed position in which the moveable valve member seats against the valve seat to seal against fluid leakage from the pump chamber to the intake port and an open position in which at least part of the moveable valve member is spaced away from the valve seat to permit fluid to flow from the intake Port to the pump chamber, the valve seat being an annular shoulder and the valve member being a flexible disc; the flexible disc has a center portion and a circular peripheral edge around the center portion, and in the open position of the check valve the peripheral edge is spaced away from the valve seat.
2. The pump of claim 1, wherein: the peripheral edge of the disc rests on the annular shoulder in the closed position of the check valve.
3. The pump of claim 1, wherein: the check valve has a center protrusion that is secured stationary in the intake fluid flow path and the center protrusion supports the flexible disc at the center portion of the disc.
4. The pump of claim 3, wherein: the protrusion is secured stationary in the intake port.
5. The pump of claim 3, wherein: the protrusion is press fit into the intake port.
6. The pump of claim 3, wherein: the peripheral edge of the disc is free to move relative to the protrusion.
7. The pump of claim 3, wherein: a plurality of liquid channels are arranged around the protrusion and define a part of the intake fluid flow path providing fluid communication between the intake port and the pump chamber.
8. The pump of claim 7, wherein: the check valve includes a base that is press fit into the intake port and the protrusion and the disc are supported by the base.
9. The pump of claim 8, wherein: the plurality of liquid channels bypass the base.
10. The pump of claim 8, wherein: the pump housing has a ledge surface that projects inwardly from the interior surface of the pump housing, and the base has an annular shoulder that has a bottom surface that engages the ledge surface of the pump housing to axially locate the base relative to the pump housing.
11. The pump of claim 8, wherein: a spring is contained in the pump housing and biases the piston toward the top stroke position, and the base has a shoulder that has a top surface and the spring engages the top surface to axially locate the base relative to the pump housing.
12. A manually operated reciprocating fluid pump comprising: a pump housing having a pump chamber and an intake port axially below the pump chamber; an intake fluid flow path providing fluid communication between the intake port and the pump chamber; a plunger extending axially downward into the pump chamber, the plunger having a piston thereon, the piston being reciprocally and axially slidable in the pump chamber between a bottom stroke position and a top stroke position; a check valve in the intake fluid flow path having a valve seat and a moveable valve member moveable between a closed position in which the valve member seats against the valve seat to seal against fluid leakage from the pump chamber to the intake port and an open position in which at least part of the valve member is spaced away from the valve seat to permit fluid to flow from the intake port to the pump chamber, the valve seat is an annular shoulder and the valve member is a flexible disc supported on a base that is press fit into the intake port; and, the flexible disc has a center portion that is connected to the base and is held stationary in the intake port by the base and a circular peripheral edge around the center portion, in the open position of the check valve the peripheral edge is spaced away from the annular shoulder and in the closed position of the check valve the peripheral edge rests on the annular shoulder.
13. The pump of claim 12, wherein: a plurality of liquid channels bypass the base and provide fluid communication between the intake port and the pump chamber.
14. The pump of claim 12 wherein: the check valve has a center protrusion that is centered axially relative to the pump chamber, the protrusion is connected to the center portion of the disc and connects the disc to the base.
15. The pump of claim 14, wherein: a plurality of liquid channels are arranged around the center protrusion.
16. The pump of claim 14, wherein: the disc, the protrusion and the base are a single component part that is assembled into the pump housing.
17. A manually operated reciprocating fluid pump comprising: a pump housing having a pump chamber and an intake port axially below the pump chamber; an intake fluid flow path providing fluid communication between the intake port and the pump chamber; a plunger extending axially downward into the pump chamber, the plunger having a piston thereon, the piston being reciprocally and axially slidable in the pump chamber between a bottom stroke position and a top stroke position; a check valve in the intake fluid flow path having a valve seat and a moveable valve member moveable between a closed position in which the valve member seats against the valve seat to seal against fluid leakage from the pump chamber to the intake port and an open position in which at least part of the valve member is spaced away from the valve seat to permit fluid to flow from the intake port to the pump chamber, the valve seat is an annular shoulder and the valve member is a flexible disc supported on a base that is press fit into the intake port; and, the pump housing has a ledge surface that projects inwardly into the fluid flow path and the base has an annular shoulder with a bottom surface that engages the ledge surface of the pump housing to axially locate the base relative to the pump housing.
18. A manually operated reciprocating fluid pump comprising: a pump housing having a pump chamber and an intake port axially below the pump chamber; an intake fluid flow path providing fluid communication between the intake port and the pump chamber; a plunger extending axially downward into the pump chamber, the plunger having a piston thereon, the piston being reciprocally and axially slidable in the pump chamber between a bottom stroke position and a top stroke position; a check valve in the intake fluid flow path having a valve seat and a moveable valve member moveable between a closed position in which the valve member seats against the valve seat to seal against fluid leakage from the pump chamber to the intake port and an open position in which at least part of the valve member is spaced away from the valve seat to permit fluid to flow from the intake port to the pump chamber, the valve seat is an annular shoulder and the valve member is a flexible disc supported on a base that is press fit into the intake port; and, a spring is contained in the pump housing and biases the piston toward the top stroke position, and the base has a shoulder that has a top surface and the spring engages the top surface to axially locate the base relative to the pump housing.
Patent Citations (27)
| Patent | Date | Inventor | Cited By |
|---|---|---|---|
| US2772116 | 1956-11-01 | Dobkin | |
| US3228347 | 1966-01-01 | Corsette | |
| US3237571 | 1966-03-01 | Corsette | |
| US3257961 | 1966-06-01 | Schlenker | |
| US3359917 | 1967-12-01 | Cooprider | |
| US3362343 | 1968-01-01 | Duda | |
| US3391647 | 1968-07-01 | Corsette et al. | |
| US3583605 | 1971-06-01 | Corsette | |
| US4065038 | 1977-12-01 | Magers et al. | |
| US4252507 | 1981-02-01 | Knickerbocker | |
| US4272228 | 1981-06-01 | Kutik et al. | |
| US4325500 | 1982-04-01 | Shay | |
| US4325501 | 1982-04-01 | Shay | |
| US4375266 | 1983-03-01 | Magers | |
| US4435135 | 1984-03-01 | Knickerbocker | |
| US4524888 | 1985-06-01 | Tada | |
| US4692103 | 1987-09-01 | Anderson | |
| US5267673 | 1993-12-01 | Crosnier et al. | |
| US5271513 | 1993-12-01 | Crosnier et al. | |
| US5332325 | 1994-07-01 | Crosnier et al. | |
| US5339972 | 1994-08-01 | Crosnier et al. | |
| US5363993 | 1994-11-01 | Mascitelli et al. | |
| US5401148 | 1995-03-01 | Foster et al. | |
| US5465880 | 1995-11-01 | Glynn | |
| US5704522 | 1998-01-01 | Orgeolet et al. | |
| US5794821 | 1998-08-01 | Foster et al. | |
| WOXWO96/14938 | 1996-05-01 |