Toe jack

Information

  • Patent Grant
  • 6450481
  • Patent Number
    6,450,481
  • Date Filed
    Friday, December 22, 2000
    23 years ago
  • Date Issued
    Tuesday, September 17, 2002
    21 years ago
Abstract
A relatively simple toe jack includes a base; a cylinder mounted on the base and carrying a plunger; a load carrying sleeve mounted on the plunger; a load saddle and a load engaging toe on the sleeve; and a two-stage pump carrying a reservoir mounted on the base beside the cylinder, the pump including a handle specifically shaped to fit into a lever which operates the piston of the pump. The plunger is returned to a rest position by a spring mounted in the plunger and connected to the bottom of the cylinder.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




This invention relates to a hydraulic jack and in particular to a toe jack.




2. Discussion of the Prior Art




So-called toe jacks are by no means new. In this connection reference is made to U.S. Pat. No. 2,165,367, issued to F. L. Gormley et al on Jul. 11, 1939; U.S. Pat. No. 2,412,414, issued to J. J. Mueller on Dec. 10, 1946; U.S. Pat. No. 2,469,670, issued to C. L. Thompson on May 10, 1949; U.S. Pat. No. 2,654,568, issued to W. S. Pine on Oct. 6, 1953; U.S. Pat. No. 3,081,066, issued to S. A. Murawski on March 12, 1963; U.S. Pat. No. 3,622,124, issued to K. R. Sidles et al on Nov. 23, 1971; U.S. Pat. No. 4,174,095, issued to D. L. Chipman on Nov. 13, 1979; U.S. Pat. No. 4,886,244, issued to J. Renault on Dec. 12, 1989; U.S. Pat. No. 5,048,794, issued to M. Mamessier on Sept. 17, 1991 and U.S. Pat. No. 5,524,868, issued to A. F. Decker et al on Jun. 11, 1996.




In general, existing jacks of the type in question suffer from a major problem, namely they operate at one speed. When the jack is placed under a load, it is often necessary to pump for a relatively long time before the load lifting element of the jack reaches the load. Because the load lifting element rises in small increments regardless of whether it is in engagement with the load, the pumping action must be repeated many times before the load is actually engaged and lifting starts.




Some jacks include a base, a piston securely mounted on the base, a load carrying cylinder mounted on the piston for vertical movement relative to the piston and base, and a pump body and a hydraulic fluid reservoir mounted on the cylinder. A handle connected to the pump body is used to pump hydraulic fluid from the reservoir to the cylinder. Thus, during pumping, the cylinder, the reservoir and the pump handle move upwardly as a unit with a load.




GENERAL DESCRIPTION OF THE INVENTION




An object of the present invention is to provide a relatively simple two-speed toe jack, i.e. a jack with load engaging elements which can be moved rapidly upwardly into engagement with a load and then slowly while lifting the load.




Another object of the invention is to provide a simple toe jack the bulk of which is fixedly mounted on a base, with only a piston or plunger and load carrying elements moving during a lifting operation. Thus, the center of gravity of the jack remains low, and when the jack is raised it does not become top heavy.




Accordingly, the invention relates to a hydraulic toe jack comprising:




(a) a base for supporting the jack on a support surface;




(b) a reservoir on said base for hydraulic fluid;




(c) a main cylinder on said base for receiving hydraulic fluid from said reservoir,




(d) a plunger in said main cylinder for vertical movement relative to said base, said reservoir and said main cylinder;




(e) a load carrying sleeve on said plunger for vertical movement therewith;




(f) a toe on said sleeve for engaging a load; and




(g) a two-stage pump on said base for pumping hydraulic fluid from said reservoir to said main cylinder at high volume and low pressure and at low volume and high pressure, whereby, during a pumping operation, the plunger and load carrying sleeve can be moved rapidly upwardly to engage a load and once in engagement with the load is moved slowly upwardly under high pressure.











BRIEF DESCRIPTION OF THE DRAWINGS




The invention is described below in greater detail with reference to the accompanying drawings which illustrate a preferred embodiment of the invention, and wherein:





FIGS. 1 and 2

are isometric views of a toe jack in accordance with the invention as seen from opposite sides;





FIG. 3

is a longitudinal sectional view of the toe jack of

FIGS. 1 and 2

;





FIG. 4

is an isometric view of a load carrying sleeve used in the jack of

FIGS. 1 and 2

;





FIG. 5

is a top view of the central portion of the jack of

FIGS. 1 and 2

;





FIG. 6

is an isometric view of the jack of

FIGS. 1 and 2

with the load carrying sleeve removed;





FIG. 7

is an isometric view of a toe used in the jack of

FIGS. 1 and 2

;





FIG. 8

is a cross section of a pump body used in the jack of

FIGS. 1 and 2

;





FIG. 9

is an isometric view of one end of a handle used in the jack of

FIGS. 1 and 2

;





FIG. 10

is a front view of a lever used in the jack of

FIGS. 1 and 2

;





FIG. 11

is an isometric view of the lever of FIG.


10


and one end of the handle of

FIG. 9

; and





FIG. 12

is a schematic flow diagram of a hydraulic system used in the pump body of FIG.


8


.











DESCRIPTION OF THE PREFERRED EMBODIMENT




Referring to

FIGS. 1 and 2

, a pump jack in accordance with the invention includes a substantially planar base


1


with sides


2


and an end


3


defining a recess for receiving a cylinder


4


, a toe mount or load carrying sleeve


5


, a reservoir


6


and a two-stage pump assembly generally indicated at


7


.




As best shown in

FIG. 3

the cylinder


4


is defined by a tubular body


8


with a closed bottom end


9


, which is securely mounted in a recess


10


in the top surface of the base


1


using bolts


12


. A cylindrical piston or plunger


13


is slidably mounted in the cylinder


4


. A snap ring and a washer (both designated


15


) and an annular flange


16


on the plunger


13


retain a seal


17


and a brass wear sleeve


18


on the bottom end of the plunger


13


. The top end of the plunger


13


extends through a gland nut


20


with a wiper (not shown) in the inner top end thereof. The plunger


13


is biased toward the lower, rest position shown phantom outline in

FIG. 3

by a helical spring


22


extending between screws


23


and


24


in the bottom end


9


of the cylinder


4


and in a partition


25


, respectively near the top end of the plunger


13


.




The plunger


13


carries the elongated load carrying sleeve


5


, which has a polygonal cross section. Referring to

FIG. 4

, the load carrying sleeve


5


includes a top wall


27


, a front wall


28


and a pair of side walls


29


integral with the front wall


28


. A hole


30


in the top wall


27


receives the threaded stem


32


of a disc-shaped load saddle


33


(

FIG. 3

) for securely mounting the sleeve


5


on the internally threaded upper end


34


of the plunger


13


. The rear end of the sleeve


5


is open for facilitating mounting of the sleeve on the plunger


13


and the cylinder


4


.




The sleeve


5


slides on the cylinder


4


with the plunger


13


. For such purpose, a pair of brass keys or slides


36


(

FIGS. 5 and 6

) are mounted on the inside of front corners


37


of the sleeve


5


using bolts


38


which extend through holes


39


in such corners


37


into the slides


36


. The slides


36


fit into rectangular cross section channels


41


, in the front corners of the cylinder


4


(FIG.


5


). When the cylinder


4


is actuated, the plunger


13


moves vertically carrying the sleeve


5


and the slides


36


therewith. A UHMW polyethylene wear strip


42


is attached to the interior of the front wall


28


of the sleeve


5


by bolts


43


extending through the strip


42


into threaded countersunk holes


45


in such front wall. The wear strip


42


slides in a shallow channel


46


(

FIG. 5

) in the front wall of the cylinder


4


.




A load lifting toe


48


is mounted on the front wall


28


of the sleeve


5


using bolts


49


. With particular reference to

FIG. 7

, the load lifting toe


48


is defined by a generally L-shaped body


50


, the vertical arm


51


of which includes transversely extending rear projections


52


for mating with complementary grooves in the front wall


28


of the sleeve


5


. The bolts


49


extend through holes


53


(

FIG. 4

) in the front wall


28


of the sleeve


5


into the top two projections


52


. It will be appreciated that the use of the mating projections


52


and the grooves makes the toe assembly strong and facilitates replacement of the toe


48


.




The cylinder


4


receives hydraulic fluid from the reservoir


6


via a pump body


54


. As best shown in

FIG. 8

, the reservoir


6


includes a generally cylindrical housing


55


mounted on a cylindrical post


56


(

FIG. 8

) on the body


54


. A bracket


57


(

FIGS. 1

to


3


,


5


and


6


) extending around the top end of the housing


55


attaches the latter to the cylinder


4


. A collapsible, cylindrical bladder


59


is provided in the housing


55


. The bladder


59


is retained in an erect condition by a rod


60


(FIG.


3


), the threaded bottom end


61


of which is mounted in the body


54


, and a disc


62


which receives the threaded top end


63


of the rod


60


. Clamps (not shown) extend around the top and bottom ends of the bladder


59


for retaining such ends on the post


56


and on the ring


62


.




Hydraulic fluid is pumped from the reservoir


6


into the cylinder


4


using the two-stage pump assembly


7


. The pump assembly


7


includes a piston


67


slidably mounted in a cavity or cylinder


68


in the pump body


54


. The piston


67


has a large diameter (low pressure) upper section


70


and a smaller diameter (high pressure) lower section


71


. The cavity


68


(

FIG. 8

) includes a complementary large diameter upper end


72


and a small diameter lower end


73


. The piston


67


is sealed in the cavity using O-rings


75


(

FIG. 3

) and a wiper (not shown) in the top end


76


of the cavity


68


.




The piston


67


is reciprocated in the cavity


68


by a two-part handle generally indicated at


78


(

FIGS. 1

to


3


) and a linkage defined by a triangular lever


79


and a link arm


80


. The handle


78


includes two telescopically interconnected sections


82


and


83


, one section


82


being tubular and the other section


83


being defined by a solid rod. A hand receiving loop


84


is provided on the free end of the tubular section


82


. A pin


85


extends through the other end of the section


82


into a longitudinally extending groove or keyway


86


in the other section


83


, whereby the length of the handle can be changed.




The handle


78


is adapted to be removably mounted in the lever


79


and prevents the use of any handle


78


other than the one specifically designed for the jack of the present invention. For such purpose, the free end


87


of the narrow diameter section


83


of the handle


78


has a unique shape complementary to the shape of a handle receiving recess


88


in the lever


79


. As best shown in

FIG. 9

, the free end


87


of the handle section


83


is stepped and tapers outwardly from a shoulder


89


. The recess


88


has the same shape. The recess


88


in the lever


79


is formed by sandwiching intermediate plates


91


between substantially triangular side plates


92


.




One corner of the lever


79


is pivotally connected to the pump body


54


by the link arm


80


, the top end (

FIG. 3

) of which extends into a recess


94


in the bottom of the lever and is retained therein by a pin


95


. The bottom end of the arm


80


is pivotally connected to the pump body


54


by a pin


96


extending between brackets


98


on the sides of the body


54


. The top end


99


or stem of the piston


67


extends into the recess


94


at approximately the bottom center of the lever


79


and is retained therein by a pin


101


. Generally inverted U-shaped handles


102


for lifting and positioning the pump are located on either side of the body


54


adjacent to the lever


79


.




The flow path of hydraulic fluid in the pump is described below with reference to FIG.


12


. In use the jack is placed beneath a load (not shown), to be lifted with the load saddle


33


or the toe


48


(as case may be) spaced apart from the load. The handle


78


is placed in the lever


79


and pumping is started. Upward movement of the piston


67


creates a partial vacuum in the hydraulic passages in the pump body


54


. Fluid is drawn from the reservoir


6


via passage


105


and a check valve


106


into a passage


107


connected to the upper end


72


of the cavity or cylinder


68


. At the same time, fluid is drawn from the reservoir


6


via passage


109


and a check valve


110


into a passage


111


connected to the lower end


73


of the cylinder


68


. On the down stroke of the piston


67


, the fluid is forced through one-way or check valves


113


and


114


in the lines


107


and


111


, respectively to passages


115


and


116


, which carry hydraulic fluid to the bottom end of the cylinder


4


causing the plunger


13


to rise rapidly in the cylinder. Thus, the large upper end


72


of the cylinder


68


provides for low pressure/high volume pumping, while the small lower end


73


provides for high pressure/low volume pumping. Under no load, both ends of the piston


67


force hydraulic fluid into the cylinder


4


, thus rapidly filling the latter. With this arrangement the number of strokes required to fully raise the plunger


13


is much lower than with existing jacks.




Once the pressure in the line


107


or


111


exceeds a predetermined limit, a spring actuated valve


118


in a line


119


opens to dump hydraulic fluid from the low pressure cylinder end


72


to the reservoir


6


. Any fluid leaking past the upper O-ring


75


in the piston


67


is contained by the wiper in the top end of the cavity or cylinder


68


and returned to the reservoir


6


via a drain line


120


(FIGS.


8


and


12


).




If a large number of lifts are being performed, fluid can be pumped into a line


121


in the pump body


54


via a quick disconnect


122


on the pump body


54


. The line


121


is connected by the lines


115


and


116


to the cylinder


4


. The quick disconnect (

FIG. 1

) is used to connect the line


121


to a power operated pump (not shown). The spring


22


returns the plunger


13


to the lower, rest position, when a valve


126


in a line


127


is manually opened using a knob


128


(

FIG. 2

) on one side of the pump body


54


to return hydraulic fluid from the cylinder


4


to the reservoir


6


. A bladder relief valve


130


is provided in a line


131


(

FIGS. 1 and 12

) in the body


54


for venting the reservoir to the outside in the event that the pressure in the line


127


exceeds a predetermined maximum if valve


126


has not been closed while using the external pump.




The apparatus described above is a ten ton jack with a wet weight (i.e. with the hydraulic fluid in the reservoir) of approximately fifty pounds. Because of the collapsible bladder, the pump can be operated in any orientation, e.g. sideways or even upside down. The unique pump handle to pump interface prevents the use of bastard handles which has been a safety concern in the past. The plunger is protected by the load carrying sleeve during lifting which limits or prevents malfunction due to plunger contact during normal operation.



Claims
  • 1. A hydraulic toe jack comprising:(a) a base for supporting the jack on a support surface; (b) a reservoir on said base for hydraulic fluid; (c) a main cylinder on said base for receiving hydraulic fluid from said reservoir; (d) a plunger in said main cylinder for vertical movement relative to said base, said reservoir and said main cylinder; (e) a load carrying sleeve on said plunger for vertical movement therewith; (f) a toe on said sleeve for engaging a load; and (g) a two-stage pump on said base for pumping hydraulic fluid from said reservoir to said main cylinder at high volume and low pressure and at low volume and high pressure, including: (i) a pump body on said base supporting said reservoir; (ii) a cavity in said pump body having a large diameter upper end and a smaller diameter lower end; (iii) a piston slidable in said cavity having a large diameter upper section for sliding in said upper end of the cavity, and a small diameter lower section for sliding in said lower end of said cavity; and (iv) a handle for manual reciprocation of said piston in said cavity, whereby, during a pumping operation, the plunger and load carrying sleeve can be moved rapidly upwardly to engage a load and, once in engagement with the load, the plunger and load carrying sleeve can move slowly upwardly under high pressure.
  • 2. The hydraulic jack of claim 1, a helical spring in said plunger, said spring connecting the plunger to the base for biasing the plunger to a rest position, whereby the plunger is returned to a rest position at the end of a lifting operation when pressure in said main cylinder is released.
  • 3. The hydraulic jack of claim 1, wherein said load carrying sleeve is polygonal in cross section including a front wall and a pair of side walls integral with said front wall.
  • 4. The hydraulic jack of claim 3, including slides in said sleeve for sliding on said main cylinder when the plunger and sleeve are moved relative to the main cylinder; and a plastic wear strip on an interior of said front wall of the sleeve; and a channel in said cylinder for slidably receiving said wear strip.
  • 5. The hydraulic jack of claim 4, wherein said pump includes a lever pivotally connected to said pump body for reciprocating said piston in said cavity; a stepped, tapered recess in said lever; and a stepped, tapered end on said handle having the same shape as said recess, whereby only a handle having a proper shape can be used to actuate the pump.
US Referenced Citations (2)
Number Name Date Kind
3081066 Murawski Mar 1963 A
5201494 Lundman Apr 1993 A