EP0000443B1

EP0000443B1 - Hydraulic jack and patient lifting device using it

Info

Publication number: EP0000443B1
Application number: EP78300132A
Authority: EP
Inventors: Raymond Clark; William T. Neill Jr.
Original assignee: Applied Power Inc
Current assignee: Enerpac Tool Group Corp
Priority date: 1977-07-08
Filing date: 1978-07-07
Publication date: 1981-11-18
Also published as: EP0000443A1; US4144713A; ES476720A1; ES471557A1; IT7850184A0; DE2861330D1; IT1105247B; BE868848A

Description

The present invention relates to hydraulic jacks comprising a ram, a reservoir, a pump with a manually-operable handle for drawing fluid from the reservoir on a suction stroke and delivering fluid to the ram on the delivery stroke, and a return valve openable by the handle to allow return of fluid from the ram to the reservoir. Such a hydraulic jack is described in U.S. Patent Specification No. 3,806,091. In that specification the opening of the valve by the handle is effected by advancing the handle through a socket in which it is mounted to engage with an actuating button connected to the release valve.
The present invention is particularly concerned with the use of hydraulic jacks in patient-lifting devices. In such devices and other devices employing hydraulic jacks the requirement for a movement of the handle to operate the release valve which is different in character from the normal pumping movement presents difficulties.
Patient lifting devices are in common use in hospitals, nursing homes, and in the homes of invalids, and they take on many different specific forms dictated by their specific function. Broadly speaking, however, such devices of the type to which the subject invention is applicable comprise an upright member of one type or another, a boom pivotably mounted on the upright member, a fluid cylinder or hydraulic ram pivotably mounted between the upright member and the boom, a fluid reservoir, and a manually operated pump used to force fluid from the reservoir into the chamber of the fluid cylinder in order to raise the boom. Of course, means must also be provided for transferring the fluid back to the reservoir from the chamber of the cylinder when it is desired to lower the boom. In the past, such means have required the person using the device either to release the pump handle or to use his other hand to actuate a separate toggle or button. Either option is, however, undesirable, for the person using the device is typically using his or her other hand to steady the patient being lifted by the device and his or her attention is too much on that patient for it to be convenient to release the handle and to reach for a separate toggle or button. An example of the type of device described above is shown in U.S. Patent Specification No. 3,222,029. In the device described in that specification a separate control knob is provided to control the lowering of the boom. For the reasons explained this is not satisfactory. In accordance with the present invention a valve means for controlled return of hydraulic fluid from the ram to the reservoir is operable by movement of the pump handle in its non-working direction to a position beyond that corresponding to the end of the normal suction stroke of the pump.
It is known in connection with hydraulic jacks to use movement of a pumping lever beyond a normal end position in order to open a direct connection between the ram cylinder and the reservoir for controlled return of the hydraulic fluid. An example of such a mechanism is described in U.S. Patent Specification No. 3,260,051. However, in the mechanism described in that specification, as in other mechanisms using this principle of operation, it is necessary to complete the delivery stroke of the pump and then go beyond this end position to release hydraulic fluid from the ram. If such a mechanism were used in a patient lifting device it would mean lifting the patient further before the boom could be lowered. This could be dangerous to the patient where, for example, treatment equipment is arranged above the patient and further lifting would bring the patient into contact with the equipment.
The invention will now be described in more detail with the aid of an example illustrated in the accompanying drawings, in which:-

FIGURE 1 is a perspective view of a patient lifting device in accordance with the invention,
FIGURE 2 is a side view, partly in section of a fluid cylinder, pump, and fluid reservoir forming part of the device of Fig. 1,
FIGURE 3 is a view along the line 3-3 in Fig. 2,
FIGURE 4 is a side view in section and on an enlarged scale of part of the mechanism shown in Fig. 2, showing the release mechanism in its non-actuated position,
FIGURE 5 is a view similar to Fig. 4, but showing the release mechanism in its actuated position, and
FIGURE 6 is a fragmentary view on a greatly enlarged scale and in somewhat simplified form of a portion of the release mechanism in its actuated position.

FIGURE 1 shows a patient lifting device comprising an upright member 10, a boom 12 pivotably mounted on the upright member 10, a fluid cylinder or hydraulic ram 14 one end of which is connected to the upright member 10 and the other end of which is connected to the boom 12, and a manually operated pump 16 operatively associated with the fluid cylinder 14 such that operation of the pump 16 causes actuation of the cylinder. The patient lifting device also comprises a reservoir 18 (shown in FIGURES 2, 4, and 5) for fluid to operate the ram 14. A patient 20 is shown seated in a conventional sling chair 22 suspended from the outer end of the boom 12. The ram 14 is pivotably mounted at at least one end (shown as the upper end in FIGURE 1), and actuation of the ram 14 raises the boom 12 and can be used to lift the patient 20. In addition, the upright member 10 can be journalled in the base 24 for at least limited rotation, permitting the patient to be swung in an arc about the upright member 10 by means of the handle 26.
The pump 16 comprises a handle 28, means defining a transfer chamber 30, and a pumping piston 32 activated by the handle 28 and operatively associated with the reservoir 18 and the transfer chamber 30 such that operation of the pumping piston 32 in one direction opens a valve 34 located at the inlet of the transfer chamber 30 and draws fluid from the reservoir 18 into the transfer chamber 30 and operation of the pumping piston 32 in the other direction closes the valve 34 and forces fluid from the transfer chamber 30 into the chamber 36 of the fluid cylinder 14. A valve 38 is located at the outlet to the transfer chamber 30, and the outlet is in communication via a conduit 40 with the chamber 36. A loose pin 42 is located in the transfer chamber 30 between the valves 34 and 38 to prevent the valve 34 from moving above the opening 43 of the pumping piston 32 into the transfer chamber 30. Instead of the illustrated pin 42, a weak compression spring could be used for this purpose.
For transferring fluid from the chamber 36 to the reservoir 18 a second transfer chamber 44 is in fluid communication with the transfer chamber 30, the chamber 36, and the reservoir 18. A compression spring 46 is located in the transfer chamber 44 so as to bear against the valve 38 and bias it towards its closed position. A valve 48 is located at the outlet of the transfer chamber 44. Means 50 are actuated by the handle 28 to open the valve 48 when the handle is in position to cause transfer of fluid from the chamber 36 to the reservoir 18. As is apparent from the drawings, the combination of the spring 46 and the position of the pumping piston 32 when the handle 28 is in contact with the means 50 ensures that the valve 38 is closed when the handle 28 is in position to cause transfer of fluid from the chamber 36 to the reservoir 18.
As best seen in FIGURE 6, the transfer chamber 44 is preferably divided into two parts, an outer chamber 51 and an inner chamber 52, by means mounted within the transfer chamber 44. At least one small hole 54 allows the restricted flow of fluid into the inner chamber 52, and the valve 48 is located at the outlet of the inner chamber 52. A compression spring 56 is located in the inner chamber 52 so as to bear against the valve 48 and bias it towards its closed position.
The means 50 comprises a plunger 58 which is biased outwardly by a compression spring 60 and which is forced inwardly to open the valve 48 by contact with the handle 28 when it is brought beyond its usual pumping position. A conduit 62 leads from the valve 48 to the reservoir 18, and it is sized at at least one point along its length to allow the restricted flow of fluid from the transfer chamber 44 to the reservoir 18 when the valve 48 is open. Preferably, and as best seen in FIGURE 6, the plunger 58 passes through at least a portion of the conduit 62, thereby further reducing the effective cross-sectional area of the conduit.
It should be noted that, while the reservoir 18 has been shown as a separate chamber surrounding the fluid cylinder 14, it could equally well be placed elsewhere, or it could simply be the volume within the cylinder on the opposite side of the cylinder head from the chamber 36.
In use, pulling the handle 28 upwardly by the normal amount causes the pumping piston to move downwardly, opening the valve 34 and drawing fluid (normally oil) from the reservoir 18 into the transfer chamber 30. During this suction stroke the valve 38 is closed. Pushing the handle 28 downwardly then causes the pumping piston to move upwardly in its delivery stroke, closing the valve 34, opening the valve 38, and forcing fluid from the transfer chamber 30 into the transfer chamber 44. Since the valve 48 is closed all during this operation, the fluid flows from the transfer chamber 44, through the conduit 40, and into the chamber 36, where it causes the ram 14 to extend. When it is desired to contract the ram 14, the handle 28 is brought into contact with the plunger 58, opening the valve 48. At that point, the valve 34 is open, but the valve 38 is closed. The combined weight of the boom and anyone being carried by the boom then causes the fluid to flow from the chamber 36, through the conduit 40, into the outer chamber 51, through the hole 54, into the inner chamber 52, through the conduit 62, and into the reservoir 18. The fact the hole 54 and the conduit 62 are of restricted cross-sectional areas, however, ensures that the lowering operation is gradual, so that no harm will come to the patient even if the plunger 58 is actuated accidentally by too vigorous movement of the handle 28.

Claims

1. A patient lifting device comprising a boom (12) pivotally mounted on an upright support (10) and liftable by means of a hydraulic ram (14) which can be supplied with hydraulic fluid from a reservoir (18) by means of a pump (16) operable manually by a pump handle (28) and from which the fluid can be returned to the reservoir to lower the boom by operation of a return valve characterized in that the return valve (48 to 60) is operable by movement of the pump handle (28) in its non-working direction to a position (Fig. 5) beyond that corresponding to the end of the normal suction stroke of the pump.

2. A device as claimed in Claim 1 in which the pump (16) communicates with reservoir (18) and the ram chamber (36) through respective one-way valves (34 and 38) characterized in that the return valve (48 to 60) controls a return passage (62) separate from the flow path controlled by the said one-way valves (34 and 38).

3. A device as claimed in Claim 1 or 2 characterized in that the return valve (48 to 60) comprises a spring loaded ball (48) and a plunger (58) for displacing said ball from its seat.

4. A device as claimed in Claim 3 characterized in that the plunger (58) extends through a restricted passage (62) reducing the rate of flow of fluid through the return valve.

5. A device as claimed in Claim 3 or 4 characterized in that the ball (48) controls an outlet from one end of a transfer chamber (44) whose other end has a one-way valve (38) for admitting fluid to the ram chamber (36) by way of a passage (40) communicating with the transfer chamber.

6. A device as claimed in Claim 5 characterized by an inner chamber (52) within the transfer chamber (44), the inner chamber having the ball (48) at its outlet and communicating with the transfer chamber through a restricted opening.

7. A device as claimed in Claim 6 characterized in that the inner chamber (52) contains a spring (56) biassing the ball (48) against its seat.

8. A hydraulic jack comprising a ram (14), a reservoir (18) a pump (16) with a manually operable handle (28) for drawing fluid from the reservoir on a suction stroke and delivering fluid to the ram on a delivery stroke, and a return valve (48 to 60) openable by the handle (28) to allow return of fluid from the ram to the reservoir characterized in that the pump handle (28) is movable in its non-working direction to a position (Fig. 5) beyond the end of the normal suction stroke of the pump and by that movement opens the return valve.

9. A hydraulic jack as claimed in claim 8 characterized by a transfer chamber (30) having non-return valves (34 and 38) as its inlet and outlet through which fluid is pumped to the ram, a second transfer chamber (44) defined between the non-return valve (38) at the outlet of the first transfer chamber and the return valve (48), which is disposed at the outlet of the second transfer chamber, and actuating means (50) operable by the handle (28) to open the return valve to allow return of fluid to the reservoir.

10. A hydraulic jack as claimed in claim 9 characterized by an inner chamber (52) within said second transfer chamber, the return valve being at the outlet of the inner chamber and there being at least one small hole (54) allowing a restricted flow from the second transfer chamber into the inner chamber.

11. A hydraulic jack comprising:

(a) a fluid cylinder (36);

(b) a reservoir (18) for fluid to operate said fluid cylinder;

(c) a manually operated pump operatively associated with said fluid cylinder and said reservoir such that operation of said pump causes extension of said cylinder, said pump comprising:

(i) a handle (28);

(ii) first means defining a first transfer chamber, said first means including a first valve at the inlet to said first transfer chamber and a second valve at the outlet of said first transfer chamber;

(iii) a pumping piston (32) activated by said handle and operatively associated with said reservoir and said first transfer chamber such that operation of said pumping piston in one direction opens said first valve (34) and draws fluid from said reservoir into said first transfer chamber (30) and operation of said pumping piston in the other direction closes said first valve and forces fluid from said first transfer chamber into the chamber of said fluid cylinder; and

(d) second means activated by said handle for transferring fluid from the chamber of said fluid cylinder to said reservoir, by more than normal motion of the handle (28) in its non-working direction, said second means comprising:

(i) third means defining a second transfer chamber (44) said third means including said second valve (38), which is located between said first and second transfer chambers, and a return valve (48) at the outlet of said second transfer chamber;

(ii) fourth means (46) for closing said second valve when said handle is in position to cause transfer of fluid from the chamber of said fluid cylinder to said reservoir; and

(iii) actuating means (50) actuated by said handle for opening said return valve when said handle is moved beyond its normal end position on the suction stroke, thereby causing transfer of fluid from the chamber of said fluid cylinder to said reservoir without further extending the fluid cylinder.

12. A hydraulic jack as claimed in claim 11 wherein said third means further comprises sixth means defining an inner chamber (52) within said second transfer chamber, said sixth means containing at least one small hole (54) allowing a restricted flow of fluid into said inner chamber and said return valve being located at the outlet of said inner chamber.

13. A hydraulic jack as claimed in claim 10 or 12 characterized by means (56) in the inner chamber biassing the return valve towards the closed position.

14. A hydraulic jack as claimed in claim 9, 10, 11, 12 or 13 in which the actuating means comprises an outwardly-biassed plunger (50) which is forced inwardly to open the return valve when the handle is in position to cause transfer of fluid to the reservoir.

15. A hydraulic jack as claimed in claim 14 characterized by a conduit (62) leading from the return valve to the reservoir, the conduit being sized at at least one point along its length to allow a restricted flow of fluid from the second transfer chamber to the reservoir when the return valve is open.

16. A hydraulic jack as claimed in claim 15 characterized in that the plunger (50) passes through at least a portion of the conduit (62).

17. A hydraulic jack as claimed in any of claims 9, 10 and 13 to 16 in which the second transfer chamber contains a biassing spring (46) for the non-return valve (38) at the outlet of the first transfer chamber (30).