Two stage grease gun

A portable grease gun with a dual pressure output capability which can be selectively changed by the user with little effort. A larger diameter plunger is longitudinally coupled to an extension. The larger diameter plunger and its extension are variable in length by manual rotation of the extension relative to the larger diameter plunger. The larger diameter plunger is slidable within a plunger retainer over a limited range and is not free to rotate within the plunger retainer. The larger diameter plunger and the plunger extension have aligned bores through them in which a smaller diameter plunger is slidable. The smaller diameter plunger moves when an actuating lever is operated to compress grease in the grease gun. The larger diameter plunger may be adjusted to remain static during operation of the actuating lever or it may be adjusted to move during all or part of the compression stroke of the actuating lever.

BACKGROUND OF THE INVENTION

The present invention pertains to portable grease guns, whether manually operated or driven by air power or by electric batteries. Typical hand operated grease guns include a piston which forces grease from a nozzle, the grease being fed to the compression chamber from an attached mounted barrel containing bulk grease or a grease cartridge. Most existing grease guns provide only one output pressure of the grease expressed from the gun.

Frequently the user of a grease gun encounters a grease zerk which will not accept grease because it is seized or clogged. In that case, little can be done without replacing the zerk to correct the problem. One prior art grease gun requires changing position of the handle to adjust the mechanical advantage. This device cannot provide the 5:1 ratio pressure increase needed to overcome a resistant zerk. Another prior art grease gun uses a complex labyrinth and a mechanical switch to engage or disengage a ball check valve to vary pressure of grease exiting the grease gun. This device does not permit supply to the grease gun from an attached barrel and therefore the portability and versatility of the device is limited.

The foregoing problems are addressed by the present two stage grease gun invention.

BRIEF SUMMARY OF THE INVENTION

A portable grease gun is provided with a dual pressure output capability which can be selectively changed by the user with little effort. The grease gun includes a plunger assembly which includes a larger diameter volume plunger which is selectively coupled longitudinally to a plunger extension by screw threads. The length of the volume plunger with the plunger extension attached may be varied by inserting the extension into the bore of the volume plunger a greater or lesser amount. This is accomplished by rotating the plunger extension relative to the volume plunger thereby moving the coupled end of the plunger extension in and out of the screw threads within the bore of the volume plunger. The volume plunger and its plunger extension are received in a longitudinal passageway of a plunger retainer which limits the longitudinal movement of the volume plunger, and prevents rotational movement of the volume plunger relative to the plunger retainer. A smaller diameter pressure plunger is slidable within the bore through the volume plunger and the attached plunger extension. The plunger assembly is longitudinally received within a bore of the grease gun body.

An actuating lever is pivotal upon the grease gun body which includes the plunger assembly within the longitudinal bore through the body. The lever includes a push block which abuts the plunger assembly to urge the pressure plunger and selectively the volume plunger toward the output orifice of the grease gun.

The desired pressure of the grease expelled from the grease gun body is controlled by selective rotation of the plunger extension to shorten or extend the effective length of the volume plunger and plunger extension combination. When the plunger extension is maximally received into the bore of the volume plunger, the volume plunger is prevented from longitudinal travel. However, the smaller diameter pressure plunger may slide along the bores of the volume plunger and the plunger extension, traveling into the compression chamber to pressurize grease at a high pressure and low volume. When the plunger extension is minimally received within the bore of the volume plunger, the effective length of the volume plunger and plunger extension combination is increased, allowing the volume plunger to be moved into the compression chamber when the push block of the actuating lever applies force to the end of the pressure plunger and the plunger extension, causing both the volume plunger and the pressure plunger to move in concert.

When the plunger extension is moved to an intermediate insertion within the bore of the volume plunger, the actuation of the lever will first cause movement of the pressure plunger alone, providing a high pressure grease delivery during the first part of the stroke of the actuating lever and subsequently a low pressure grease delivery when the push block begins to abut the plunger extension and the pressure plunger together, thereby urging both the pressure plunger and the volume pressure together toward the output body of the grease gun. The grease gun can therefore be used to apply high pressure grease to a resistant zerk during the first part of the stroke of the actuating lever and then to deliver high volume grease at low pressure after the resistance of the zerk is overcome.

It is a primary object of the invention to provide a portable grease gun which can be adjusted to deliver grease at high pressure and low volume or at low pressure and high volume. It is a further object of the invention to provide a portable grease gun which can be adjusted to overcome a clogged or seized zerk and then to inject grease into the corrected zerk at lower pressure and higher volume. It is also an object of the invention to provide a grease gun which is easily adjusted for pressure output by the user without tools. It is an additional object of the invention to provide an easily manufactured grease gun which will expel grease at more than one pressure.

DETAILED DESCRIPTION OF THE INVENTION

Reference is drawn toFIGS. 1-8and specifically toFIG. 1, initially.FIG. 1discloses a grease gun body1according to the present invention with the plunger assembly27thereof shown in exploded view. Plunger assembly27is received within longitudinal bore28of grease gun body1. Plunger assembly27comprises a volume plunger3which is slidably received within an elongate hollow cylindrical plunger retainer9. Plunger retainer9is provided with an opening29on its sidewall30into which guide pin17is received. Volume plunger3includes an elongate slot31into which guide pin17may extend such that volume plunger3is prevented from rotation relative to plunger retainer9, while remaining free to move longitudinally within plunger retainer9over a range limited by a stop within plunger retainer9.

O-ring23and backup ring25are received on inner end32of plunger retainer9. Opposing outer end33of plunger retainer9is threaded to be received in threaded bore28. Slots56are provided on outer end33to aid threading plunger retainer9into bore28.

Plunger extension11is received in longitudinal bore36of plunger retainer9and is coaxially retained to volume plunger3, at a selected depth, by selective insertion of inner end34of plunger extension11into passageway35of volume plunger3. Threads55on inner end34of plunger extension11mate with internal threads54within passageway35of volume plunger3. Plunger extension11with volume plunger3attached coaxially thereto is biased toward push block4by volume plunger spring12. Bearing ring18provides a sliding surface between shoulder53of plunger extension11and volume plunger spring12.

By rotating plunger extension11clockwise or counterclockwise, the effective length of the coaxially connected plunger extension11and volume plunger3may be selected. Thumb wheel48on plunger extension11facilitates rotation thereof by the user.

Pressure plunger2is slidably received within the longitudinal bore37of plunger extension11and the longitudinal passageway35of volume plunger3and is biased toward push block4by pressure plunger spring13. Pressure plunger2comprises inner end41from which extends needle42having pressure face43on free end44thereof.

Volume plunger3is slidable over a limited range within the longitudinal bore36of plunger retainer9. Guide pin17is received in sidewall30of plunger retainer9and rides in slot31of volume plunger3.

The range of longitudinal retroactive movement of volume plunger3is limited by an internal stop57(seeFIG. 6) spaced apart from inner end32of plunger retainer9. Volume plunger3comprises a counterbore50extending from outer end49part way therethrough. Counterbore50accommodates inner end34of plunger extension11while the remainder of passageway35is reduced in size to accommodate body38of pressure plunger2for sliding movement therealong.

To reach into and be slidable within passageway35of volume plunger3, pressure plunger must pass along bore37of plunger extension11. Pressure plunger spring13biases head39of pressure plunger2longitudinally outward along bore37while volume plunger spring12biases the interconnected plunger extension11and volume plunger3longitudinally outwardly along bore36. Inward longitudinal travel of volume plunger3is limited by contact of the thumb wheel48against outer end33of plunger retainer9.

Referring now toFIGS. 2 and 3, grease gun26further comprises an actuating lever5pivotally retained to grease gun body1by hinge pin46. Push block4is retained to actuating lever5by spring pin10allowing push block4to rotate about spring pin10in order to maintain a flat surface against outer end face40of pressure plunger2.

Handle8depends from grease gun body1at an approximate perpendicular to the longitudinal axis of grease gun body1. Output body6, which may be a nozzle, is received within longitudinal bore28grease gun body1at output end22and includes an output check ball20biased by output spring15which is retained in output body6by output check screw16.

Grease gun body1further comprises a barrel mount47which houses inlet valve body7, which includes valve spring14which biases inlet check ball21. A barrel24may be selectively mounted to grease gun body1at barrel mount47. Grease gun26is shown with the inner end34of plunger extension11substantially fully inserted into counterbore50of volume plunger3. In this condition, grease gun26is adjusted to deliver grease at a high pressure.

InFIG. 2, the grease gun26as shown is ready to begin to expel grease from compression chamber45through output body6at high pressure, that is, in the range of about 10,000 psi. Actuating lever5has been retracted from handle8allowing pressure plunger spring13to urge pressure plunger2to follow push block4as it retreats from grease gun body1as it is carried on spring pin10on actuating lever5. Volume plunger3is maximally retracted from compression chamber45while needle42of pressure plunger2remains partially within compression chamber45. Compression chamber45may be filled with grease which passes inlet check ball21from barrel24.

FIG. 3discloses the position of the plunger elements after actuating lever5has been moved back to rest against handle8. Volume plunger3remains in the same position as inFIG. 2while pressure plunger2has further protruded into compression chamber45with needle42thereof inserted within the output duct51thereby forcing grease from compression chamber45past outlet check ball20. The force upon outer end face40of pressure plunger2exerted by push block4compresses pressure plunger spring13.

Referring now toFIGS. 4 and 5, grease gun26is illustrated in condition to expel a large volume of grease at a low pressure.FIG. 4shows the location of pressure plunger2and volume plunger3when actuating lever5is maximally retracted from handle8. In the condition of grease gun26inFIGS. 4 and 5, plunger extension11has been retracted from counterbore50of volume plunger3by selective rotation of plunger extension11by manipulation of thumb wheel48thereof effectively unscrewing inner end34of plunger extension11from counterbore50. This effectively extends the length of the combined volume plunger3and plunger extension11, allowing outer end52of plunger extension11to extend from longitudinal bore28and from plunger retainer9. As should be understood, as actuating lever5starts to move toward handle8, push block4forces both pressure plunger2and volume plunger3toward output body6across compression chamber45. This movement causes volume plunger3combined with pressure plunger2to force a large volume of grease at low pressure past output check ball20against output spring15.

After actuating lever5has been fully rotated into abutment on handle8, as shown inFIG. 5, volume plunger3as well as pressure plunger2have traversed compression chamber45toward output duct51causing low pressure grease to pass along output duct51and pass output check ball20of output body6.

FIGS. 6-8illustrate the adjusted position of grease gun26in which plunger extension11is mounted to volume plunger3midway into counterbore50thereof. By selective rotation of plunger extension11by manipulation of thumb wheel48, inner end34may be moved into an intermediate position along counterbore50of volume plunger3. In this position grease gun26is capable of delivering grease at high pressure or at high volume depending on the extent of retraction of the actuating lever5. Specifically, inFIG. 6, actuating lever5is shown fully retracted such that grease gun26is ready to expel grease at high pressure, such as when a resistant zerk must be overcome. Volume plunger3is stationed at a rest position determined by the retractive urging created by volume plunger spring12as limited by internal stop57of plunger retainer9. Pressure plunger2is retracted from output body6by the urging of pressure plunger spring13but such retraction is limited by the abutment of head39thereof against push block4.

As seen inFIG. 7, as actuating lever5has moved from a fully retracted position partway toward handle8, pressure plunger2has been urged into compression chamber45while volume plunger3has remained in its rest position as seen inFIG. 6. As needle42of pressure plunger traverses compression chamber45, grease therein is forced at high pressure past output check ball20to be expelled into a zerk (not shown) which would be inserted into a coupler and extension (not shown) attached to output body6proximal to output check screw16. Therefore, high pressure grease could be forced into a resistant zerk to overcome its clog or seizure. From the position of actuating lever5seen inFIG. 7, grease gun26is in condition to deliver grease at low pressure as actuating lever5continues to be moved toward handle8.

FIG. 8illustrates the position of volume plunger3and pressure plunger2after actuating lever5has completed its travel and come into abutment with handle8. Volume plunger3has advanced substantially into compression chamber45coincident with movement of pressure plunger2, with plunger assembly27propelling grease from compression chamber45through output body6at high volume and low pressure.

Therefore it should be understood that grease gun26may be adjusted to deliver grease at high pressure and low volume when inner end34of plunger extension11is maximally inserted into counterbore50of volume plunger3. However, when inner end34of plunger extension11is minimally inserted into counterbore50of volume plunger3, grease gun26will expel grease at low pressure and high volume. Furthermore, plunger assembly27may be adjusted such that a first portion of the stroke of actuating lever5from its fully retracted position will deliver grease at high pressure while a remaining portion of the stroke of the actuating lever5will deliver grease at low pressure. This adjustment is made by varying the depth of insertion of inner end34of plunger extension11into counterbore50of volume plunger. By selective adjustment, the proportion of stroke of the actuating lever5which causes the grease gun26to deliver high pressure grease may be varied, that is, the shorter the effective length of the combination of the volume plunger3and the plunger extension11, the larger the proportion of stroke of the actuating lever5from its fully retracted position which will deliver high pressure grease from grease gun26. As the effective length of the volume plunger3and plunger extension11increases, the smaller the proportion of the stroke of actuating lever5from full retraction will be which causes the grease gun26to deliver high pressure grease, with the remainder of the compression stroke of actuating lever5toward handle8causing low pressure grease to be expelled from grease gun26.

The foregoing description of the invention has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise form disclosed. Modifications and variations of the embodiments are possible in light of the above disclosure or such may be acquired through practice of the invention. The embodiments illustrated were chosen in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and by their equivalents.