The present disclosure relates to a hydraulic valve and control system that can be used, for example, in a patient handling apparatus, such as emergency cot, medical bed, stretcher, stair chair, or other apparatuses that support a patient where increased speed of a component, such as a hydraulic cylinder used to move the base of a patient handling apparatus, is desired.
For example, when a patient handling apparatus, such as an emergency cot, is to be loaded into an emergency vehicle, such as an ambulance, the patient handling apparatus is moved to the rear of the emergency vehicle where it is then at least partially inserted into the compartment so that it is initially supported on one end, for example, by its head end wheels resting on the compartment floor. Alternately, the cot may be moved onto a loading arm or arms, which extend from the emergency vehicle into the cot and fully support the cot, but do not interfere with the lifting mechanism. In any case, once the cot is supported (either by the head end wheels or a loading arm or loading arm(s)), the base can be raised to allow the cot to then be fully loaded in to the emergency vehicle. The faster the base can be raised, the faster the patient handling apparatus can be loaded into the vehicle, and the quicker the patient weight can be unloaded from a caregiver and transferred to the emergency vehicle, which significantly reduces the stress and strain on a caregiver. The increase speed also increases the speed at which the patient can be handled and delivered to the medical facility, typically an emergency room. Therefore, quick retraction of the base can be significant to the caregiver in all cases and even more significant to the patient in some cases.
Accordingly, there is a need to provide a patient handling apparatus with a hydraulic valve and control system that can quickly move one component relative to another component, such as an emergency cot's base relative to the cot's frame without inducing an unacceptable increase in pressure in the hydraulic cylinder that is doing the work.
Accordingly, a hydraulic valve and control system is disclosed that can move one hydraulic component relative to another hydraulic component more quickly when needed.
In one embodiment, an apparatus includes a hydraulic circuit. The hydraulic circuit is configured to selectively open fluid communication between one portion of the hydraulic circuit and another portion of the hydraulic circuit based on the flow of the hydraulic fluid in the one portion. When the flow of hydraulic fluid exceeds a selected threshold in the one portion of the hydraulic circuit, the flow of fluid urges the opening of a hydraulic component of the hydraulic circuit to allow communication between the one portion and the other portion of the hydraulic circuit.
For example, the one portion of the hydraulic component comprises a pilot operated control valve. The pilot operated control valve has a first chamber with a first inlet, a second inlet, an outlet, and a pilot piston assembly mounted for movement in the first chamber. The pilot piston assembly includes a pilot piston with a piston side facing the first inlet and a pilot rod that extends from the first chamber into a second chamber, which is sealed from the first chamber. The second inlet is in fluid communication with the outlet of the first chamber so that fluid flows from the outlet of the first chamber during all fluid flow conditions. The second chamber includes an inlet, an outlet, and a valve poppet movably mounted in the second chamber between a closed position wherein the inlet of the second chamber is not in fluid communication with the outlet of the second chamber and one or more open positions wherein the inlet of the second chamber is in fluid communication with the outlet of the second chamber. When the fluid flow to the first inlet of the first chamber exceeds a preselected flow rate, back pressure at the inlet of the first chamber will move the pilot piston and cause the pilot rod to move the valve poppet from its closed position to one of its open positions to allow fluid flow from the inlet of the second chamber to the outlet of the second chamber.
In another embodiment, a pilot operated control valve includes a first chamber with a first inlet, a second inlet, an outlet, and a pilot piston assembly mounted for movement in the first chamber. The pilot piston assembly includes a pilot piston with a piston side facing the first inlet and a pilot rod that extends from the first chamber into a second chamber, which is sealed from the first chamber. The second inlet is in fluid communication with the outlet of the first chamber so that fluid flows from the outlet of the first chamber during all fluid flow conditions. The second chamber includes an inlet, an outlet, and a valve poppet movably mounted in said chamber between a closed position wherein the inlet of the second chamber is not in fluid communication with the outlet of the second chamber and one or more open positions wherein the inlet of the second chamber is in fluid communication with the outlet of the second chamber. When the fluid flow to the first inlet of the first chamber exceeds a preselected flow rate, back pressure at the inlet of the first chamber will move the pilot piston and cause the pilot rod to move the valve poppet from its closed position to one of its open positions to allow fluid flow from the inlet of the second chamber to the outlet of the second chamber.
For example, in one aspect, the pilot operated control valve includes a valve body, such as a cylindrical valve body, with the first and second chambers located in the valve body.
In a further aspect, the second inlet is formed in the valve body. For example, the second inlet may be formed by two or more orifices formed in the valve body wall.
In another embodiment, the second inlet is formed by a passageway through the pilot piston.
In yet another embodiment, an apparatus includes a hydraulic circuit and a hydraulic cylinder. The hydraulic cylinder has a rod, a cap end chamber, and a rod end chamber. The hydraulic circuit is operable to direct the flow of hydraulic fluid between a pump, the hydraulic cylinder, and a reservoir. Further, the hydraulic circuit is configured to selectively open fluid communication between one chamber of the hydraulic cylinder and the reservoir based on the flow condition of the hydraulic fluid flowing to the other chamber of the hydraulic cylinder to thereby allow faster evacuation of the hydraulic fluid from the one chamber of the hydraulic cylinder.
In one aspect, the hydraulic circuit is configured to selectively open fluid communication between the cap end chamber of the hydraulic cylinder and the reservoir to allow the hydraulic fluid to be quickly exhausted from the cap end chamber based on the flow condition of the hydraulic fluid flowing to the rod end chamber of the hydraulic cylinder.
According to yet another form of the disclosure, a patient handling apparatus includes a hydraulic circuit and a hydraulic cylinder to raise or lower a component of the patient handling apparatus. The hydraulic cylinder has a rod, a cap end chamber, and a rod end chamber. The hydraulic circuit is operable to direct the flow of hydraulic fluid between a pump, the hydraulic cylinder, and a reservoir. Further, the hydraulic circuit is configured to selectively open fluid communication between one chamber of the hydraulic cylinder and the reservoir based on the flow condition of the hydraulic fluid flowing to the other chamber of the hydraulic cylinder to thereby allow faster evacuation of the hydraulic fluid from the one chamber of the hydraulic cylinder.
In one aspect, the patient handling apparatus includes a frame, a base, and a lift assembly supporting the frame relative to the base. The hydraulic cylinder is configured to extend or retract the lift assembly to thereby raise or lower the base or the frame with respect to the other.
In yet another aspect, the hydraulic circuit includes a control valve to control the fluid communication between the cap end chamber and the reservoir, and the hydraulic circuit is configured to selectively open the control valve to allow fluid to evacuate at least some of the hydraulic fluid from the cap end chamber to the reservoir based on the flow condition of the hydraulic fluid flowing to the rod end chamber. For example, the hydraulic circuit is configured to selectively open the control valve when there is a high flow condition to the rod end chamber of the hydraulic cylinder to thereby allow faster evacuation of the hydraulic fluid from the cap end chamber of the hydraulic cylinder.
In other aspects, the control valve is a pilot operated control valve that includes a first chamber with a first inlet, a second inlet, an outlet, and a pilot piston assembly mounted for movement in the first chamber. The pilot piston assembly includes a pilot piston with a piston side facing the first inlet and a pilot rod that extends from the first chamber into a second chamber, which is sealed from the first chamber. The second inlet is in fluid communication with the outlet of the first chamber so that fluid flows from the outlet of the first chamber during all fluid flow conditions. The second chamber includes an inlet, an outlet, and a valve poppet movably mounted in the second chamber between a closed position wherein the inlet of the second chamber is not in fluid communication with the outlet of the second chamber and one or more open positions wherein the inlet of the second chamber is in fluid communication with the outlet of the second chamber. When the fluid flow to the first inlet of the first chamber exceeds a preselected flow rate, back pressure at the inlet of the first chamber will move the pilot piston and cause the pilot rod to move the valve poppet from its closed position to one of its open positions to allow fluid flow from the inlet of the second chamber to the outlet of the second chamber.
In another embodiment, a method of loading a patient handling apparatus from a cargo area of an emergency vehicle includes moving the patient handling apparatus adjacent an opening to the cargo area of an ambulance and supporting the litter frame of the patient handling apparatus in a manner such that the base is free to be raised relative to the litter frame (and hence deck). The method further includes directing hydraulic fluid at a high flow rate to the rod end of the lift assembly hydraulic cylinder and, based on that high flow rate, directing at least some of the hydraulic fluid from the cap end of the hydraulic cylinder to a reservoir, to thereby allow faster discharge or evacuation of the hydraulic fluid from the cap end chamber of the hydraulic cylinder.
Accordingly, the present disclosure provides a hydraulic valve and hydraulic circuit that can improve the control over the movement of a component of an apparatus, such as a patient handling apparatus, and further allows the component to be moved quickly while maintaining acceptable pressure in the hydraulic circuit.
These and other objects, advantages, purposes and features of the disclosure will become more apparent from the study of the following description taken in conjunction with the drawings.
Referring to
Referring again to
Referring again to
In the illustrated embodiment, each load bearing member 22 comprises a telescoping compression/tension member 42. Compression/tension members 42 may be pivotally joined at their medial portions about a pivot axis to thereby form a pair of X-frames 44 (
In addition to load bearing members 22, patient handling apparatus 10 includes a pair of linkage members 50 and 52 (
As best seen in
As noted above, lift assembly 20 is extended or contracted by actuator 30. In the illustrated embodiment actuator 30 comprises a hydraulic cylinder 80, which is controlled by a control system 82. Although one actuator is illustrated, it should be understood that more than one actuator or cylinder may be used. As will be more fully described below, control system 82 includes a hydraulic circuit 90 and a controller 120, which is in communication with hydraulic circuit 90 and a user interface 120a that allows an operator to select between the lifting, lowering, and raising functions described herein. For example, user interface controls 120a may have a touch screen with touch screen areas or may comprise a key pad with push buttons, such as directional buttons, or switches, such as key switches, that correspond to the lifting, lowering, raising, and retracting functions described herein to allow the user to select the mode of operation and generate input signals to controller 120. As will be more fully described below, the controller 120 may also automatically control the mode of operation.
Referring again to
Cylinder 80 is extended or retracted by control system 82 to extend or contract lift assembly 20 and generally operates in four modes, namely (first mode) to raise the frame 12 when base 18 is supported on, for example, a ground surface (
Referring to
Referring again to
When fluid is directed to cap end chamber 84a, the rod 86 wi11 extend to raise the frame 12 relative to base 18 at a first speed. This mode of operation is used when base 18 is supported on a support surface, such as the ground, which can be detected by a controller 120 in various ways described below, It should be understood, that the first mode may also be used to lower or extend base 18 when the faster speed of the third mode described below is not appropriate or desired.
Referring to
Also provided is a second pilot operated check valve 108 connected between the valve assembly 102 and pump 92. Optionally, valves 98 and 108 are provided as a dual pilot operated check valve assembly 110 which includes both valves (98 and 108) and allows fluid flow through each respect conduit in either direction. The valves 98 and 108 of the dual pilot check valve assembly 110 are operated by the fluid pressure of the respective branch of fluid conduit (96 or 100) as well as the fluid pressure of the opposing branch of fluid conduit (96 or 100), as schematically shown by the dotted lines in
Referring to
In order to speed up the extension of rod 86 when operating in the third mode, hydraulic circuit 90 includes a third hydraulic conduit 112, which is in fluid communication with conduits 96 and 100 via a check valve 114 to thereby allow fluid communication between the cap end chamber 84a and the rod end chamber 84b and to allow at least a portion of the fluid output from the rod end chamber 84b to be redirected to the cap end chamber 84a, which increases the speed of the rod 86 (i.e. by increasing the pressure and/or fluid flow of the fluid delivered to the end cap chamber 84a).
To control (e.g. open and close) fluid communication between the cap end chamber 84a and rod end chamber 84b via conduit 112, conduit 112 includes a valve 116, such as a solenoid valve or a proportional control valve, which is normally closed but selectively controlled (e.g. opened) to open fluid communication between the rod end chamber 84b and the cap end chamber 84a as described below. As noted, this will allow at least a portion of the fluid output from the rod end chamber 84b to be redirected to the end cap chamber 84a to thereby increase the speed of rod 86. Optionally, an additional valve, (not shown) such as a solenoid valve, may be included in conduit 100, for example, between conduit 112 and pump 92, which is normally open but can be selectively controlled (e.g. closed), so that the amount of fluid (and hence fluid pressure and/or fluid flow) that is redirected from the rod end chamber 84b may be varied. For example, all the fluid output from rod end chamber 84b may be redirected to the cap end chamber 84a. In another embodiment, an additional electrically operated proportional control valve may be used in any of the branches of the conduit (e.g. 96, 100, or 112) to control the rate of fluid flow through the respective conduits and thereby control and vary the speed of the extension of rod 86.
As noted above, control system 82 includes controller 120, which is also schematically represented in
Referring again to
For example, controller 120 may control (e.g. open or close) the valve 116 to increase or stop the increased speed of cylinder 80 and/or slow or stop the pump to slow or stop the cylinder, or any combination thereof based on an input signal or signals from or the status of the sensor(s). Further, controller 120 may control (e.g. close) the valve 116 before, after, or at the same time as slowing or stopping the pump based on an input signal or signals from or the status of the sensor(s). Alternately, controller 120 may slow, increase the speed of, or stop the pump P in lieu of controlling (e.g. dosing) the valve 116 based on an input signal or signals from or the status of the sensor(s). For example, when there is no weight is sensed on the base, the motor may be configured to drive the pump at a higher speed (e.g. by increasing the motor pulse width modulation (PWM)) to generate higher fluid flow and this pressure.
As described in copending application, entitled, HYDRAULIC CIRCUIT FOR A PATIENT HANDLING APPARATUS, attorney docket no. 143667.185016 (P-619), filed on even date herewith, in one embodiment, control system 82 may include one or more sensors to detect when the base 18 of the patient handling apparatus 10 is contacting the ground or other surface, such as a bumper or another obstruction, which, as noted, may be used as an input signal or signals to the controller 120 to control the hydraulic circuit 90. Suitable sensors may include Hall Effect sensors, proximity sensors, reed switches, optical sensors, ultrasonic sensors, liquid level sensors (such as available from MTS under the brand name TEMPOSONIC), linear variable displacement transformer (LVDT) sensors, or other transducers or the like. For further details reference is made to the copending application, which is incorporated by reference herein in its entirety.
As described in the referenced application, controller 120 may control (e.g. open or close) the valve 116 to increase or stop the increased speed of cylinder 80 and/or slow or stop the pump to slow or stop the cylinder, or any combination thereof based on an input signal or signals from or the status of the sensor(s). Further, controller 120 may control (e.g. close) the valve 116 before, after, or at the same time as slowing or stopping the pump based on an input signal or signals from or the status of the sensor(s). Alternately, controller 120 may slow, increase the speed of, or stop the pump P in lieu of control (e.g. close) the valve 116 based on an input signal or signals from or the status of the sensor(s). For example, when there is no weight.
is sensed on the base, the motor may be configured to drive the pump at a higher speed (e.g. increasing the motor pulse width modulation (PWM)) to generate higher fluid flow and this pressure.
Further, in addition, or alternately, control system 82 may include one or more sensors 124 (
For example, in one embodiment, referring to
In yet another embodiment, control system 82 may include one or more sensors 126 (
Further, when multiple configurations are detected, controller 120 may compare the detected configuration of patient handling apparatus 10 to a prescribed configuration and, in response, control the hydraulic circuit 90 based on whether the patient handling apparatus 10 is in or near a prescribed configuration or not. Or when only a single configuration is detected, controller 120 may simple use the signal from the sensor as an input signal and control hydraulic circuit 90 based on the input signal.
When the patient handling apparatus 10 is no longer in the prescribed configuration (e.g. by comparing the detected configuration to a prescribed configuration stored in memory or detecting that it is not in a prescribed configuration), controller 120 may be configured to open or reopen the valve 116 to allow cylinder 80 to operate at its increased speed but then close valve 116 when controller 120 detects that patient handling apparatus 10 is in a prescribed configuration and/or, further, may slow or stop the motor to stop the pump or reverse the motor.
For example, one of the prescribed configurations may be when the lift assembly is in its transport or fully raised configuration. In this manner, similar to the previous embodiment, when controller 120 detects that patient handling apparatus 10 is near or in its fully raised configuration, controller 120 may be configured to close valve 116 so that cylinder 80 can no longer be driven at the increased speed, and further may also stop motor 94 to stop pump 92. As noted above, controller 120 may open or close the valve 116 before, after, or at the same time as stopping the pump (or reversing the motor) based on the input signal or signals from or the status of the sensor(s). Alternately, controller 120 may stop the pump 92 in lieu of closing the valve 116 based on an input signal or signals from or the status of the sensor(s).
In yet another embodiment, the control system 82 may include a sensor 128 (
So for example, if an attendant is removing patient handling apparatus from an emergency vehicle and has selected the base lowering function, and while the base is being lowered at the increased speed, controller 120 detects that the motor or pump is under an increase in load (e.g. detects an increase in current) (which, as noted, would occur when the base 18 is supported, either by a support surface or an obstruction) controller 120 may close valve 116 so that cylinder 80 will no longer be driven at the increased speed. Optionally, controller 120 may also or instead slow or stop the pump and/or stop the pump before closing the valve. Alternately, controller 120 may simultaneously close the valve 116 and slow or stop the pump. As described above, in yet another embodiment, controller 120 may close the valve 116 prior to base 18 being supported (for example, when the frame 12 or base 18 reaches a prescribed height or when apparatus 10 has a prescribed configuration) and only after controller 120 detects that base 18 has contacted the ground surface and/or the base 18 is fully lowered, controller 120 will stop pump 92 so that cylinder 80 will no longer extend. Or the controller 120 may be configured to stop the pump 92 before the base reaches the ground to avoid overshoot.
The controller 120 may also receive signals indicative of the presence of the patient handling apparatus 10 near an emergency vehicle. For example, a transducer may be mounted to the patient handling apparatus 10, and a magnet may be mounted to the emergency vehicle and located so that when the patient handling apparatus is near the emergency vehicle, the transducer will detect the magnet and generate a signal based on its detection. In this manner, when an operator has selected the base extending (e.g. lowering) function and controller 120 detects that patient handling apparatus 10 is near an emergency vehicle and, further, detects one or more of the other conditions above (e.g. that the base is not contacting a support surface or there is no load on the motor or pump or the patient handling apparatus 10 is not in a prescribed configuration), controller 120 may open valve 116 to allow the cylinder to be driven at the increased speed. In this manner, these additional input signals may confirm that the situation is consistent with a third mode operation.
Alternately, controller 120 may also receive signals indicative of the presence of the patient handling apparatus 10 in an emergency vehicle. For example, a transducer may be mounted to the patient handling apparatus 10, and a magnet may be mounted to the emergency vehicle and located so that when the patient handling apparatus is in the emergency vehicle, the transducer will detect the magnet and generate a signal based on its detection. In this manner, when an operator has selected the base lowering function and controller 12 detects that patient handling apparatus 10 is in the emergency vehicle and detects one or more of the other conditions above (e.g. that the base is not contacting a support surface or there is no load on the motor or pump or the patient handling apparatus 10 is not in a prescribed configuration), the signal indicating that patient handling apparatus 10 is in the emergency vehicle will override the detection of the other conditions and the controller 120 may maintain valve 116 closed to prevent the cylinder from being driven at the increased speed and, further, override the input signal generated by the operator. For further details of sensing the proximity to or location in an emergency vehicle, reference is made to U.S. pat. app. Ser. No. 14/998,028, entitled PATIENT SUPPORT, filed on Jul. 7, 2014 (P-433A), which is incorporated by reference in its entirety herein.
In yet another embodiment, the patient handling apparatus 10 may include a patient handling apparatus-based communication system 130 (
In one embodiment, rather than allowing controller 120 to start in the third mode (when all the conditions are satisfied), controller 120 may be configured initially start the base lowering function in the first mode, where the base is lowered at the slower, first speed. Only after controller 120 has checked that there is a change in the load (e.g. by checking a sensor, for example a load cell or current sensing sensor) on the motor or cot to confirm that the motor or pump are now under a load (which would occur once the apparatus is pulled from the emergency vehicle and the base is being lowered), does controller 120 then switch to the third mode to operate the cylinder at the fluster, second speed. Again, once operating in the third mode, should controller 120 detect one or more of the conditions noted above (base 18 is supported or encounters an obstruction, the height exceeds a prescribed height, the configuration is in a prescribed configuration, the load on the motor or pump exceeds a prescribed value) controller 120 will close valve 116 and optionally further slow or stop pump. As noted above, the valve 116 may be closed by controller 120 after the pump 92 is slowed or stopped or simultaneously.
In any of the above embodiments, it should be understood that control system 82 can control hydraulic circuit 90 to slow or stop the extension of rod 86 of cylinder, using any of the methods described above, before the conditions noted above, such as before reaching a predetermined height, before reaching a predetermined configuration, before making contact with the ground or an obstruction, or before reaching a prescribed load on the motor etc. Further, control of the fluid through the hydraulic circuit may be achieved by controlling the flow rate or opening or closing the flow using the various valves noted above that are shown and/or described. Further, as noted to avoid excess pressure in the hydraulic circuit, controller 120 may reverse the motor when controlling the valves described herein or may slow or stop the motor and pump before reaching the target (e.g. maximum height). Additionally, also as noted, controller 120 may control the hydraulic circuit by (1) adjusting the flow control valves or valves (e.g. valve 116), (2) adjusting the pump 92 (slow down or stop) or 3) adjusting both the flow control valves or valves (e.g. valve 116) and the pump, in any sequence.
Further, it should be understood, in each instance above, where it is described that the controller or sensor or other components are in communication, it should be understand that the communication may be achieved through hard wiring or via wireless communication. Further, although illustrated as discrete separate components, the various components may be assembled or integrated together into a single unit or multiple units.
Optionally, described more fully below, hydraulic circuit 90 may instead, or in addition, incorporate a hydraulic based logic component that is configured to generate a pilot signal to control another hydraulic component, such as a valve, based on flow through the hydraulic based logic component. For example, as will be described, when the flow of fluid through the hydraulic based logic component reaches a threshold value, the hydraulic based logic component will generate a pilot signal to open a pilot operated valve to divert the flow of fluid away from another hydraulic component to avoid over pressurizing or simply change the logic of the hydraulic circuit.
As noted above, the frame 12 is optionally configured to allow the frame 12 to be tilted relative to the lift assembly 20 so that one end (e.g. head-end or foot-end) of the frame 12 can be raised beyond the fully raised height of the lift assembly to allow the patient handling apparatus to be inserted more easily into the compartment of an emergency vehicle. In addition, the frame 12 can be tilted without decoupling the frame 12 from the lift assembly 20.
In the illustrated embodiment, movable foot-end upper pivot connections 24b are configured so that they can move in a direction angled (e.g. oblique (acute or obtuse) or even perpendicular) relative to the longitudinal axis 12b of the frame 12 and optionally along or relative to the longitudinal axis 12b (
Referring to
Referring again to
Thus, when lift assembly 20 starts in its lowermost position and is extended, movable foot-end upper pivot connections 24b move along guide path P from one end (which corresponds to the lowermost position of lift assembly 20) where the movement of movable foot-end upper pivot connections 24b is generally linear (and parallel to longitudinal axis 12b of frame 12) to a non-linear portion of path P, which corresponds to a raised position of lift assembly. As lift assembly 20 continues to extend and raise frame 12 further, movable foot-end upper pivot connections 24b continue to move along non-linear path P (
As best seen in
In the illustrated embodiment, guides 32 are each formed from a low friction member or plate, such as a high density polyethylene plate, mounted to frame 12. Each low friction member or plate 72 includes a recess formed therein, which forms guide path P. Alternately, guide 32 may be formed from a metal member or plate with the recess formed therein lined with a low friction material, such as high density polyethylene.
In this manner, pivot connections 26b allows telescoping members 42 to pivot about a moving horizontal axis (i.e. moving horizontal axis of transverse member 60) (moving both in the longitudinal direction and/or vertical direction, as noted above, namely along longitudinal axis 12a or toward or away from longitudinal axis 12a) and, further, allow lift assembly 20 to adjust the height of frame 12 relative to base 18.
In addition, referring again to
For further details of frame 12, telescoping members 44, base 18, brackets 54 and 56, linkage members 50 and 52, and a gatch mechanism, and other components not specifically mentioned or described herein, or for alternate embodiments of components described herein, reference is made to U.S. Pat. Nos. 5,537,700 and 7,398,571, and published Application No. WO 2007/123571, commonly owned by Stryker Corporation, which are herein incorporated by reference in their entireties.
Thus, when the ambulance patient handling apparatus is in the fully collapsed position or loading configuration, and referring to
For further optional details on how lift assembly 20 is mounted to frame 12, reference is made to copending U.S. appl. Ser. No. 15/949,624, entitled EMERGENCY COT WITH A LITTER HEIGHT ADJUSTMENT MECHANISM, attorney docket no. 143667.173860 (P-566A) and filed on Apr. 10, 2018, which is incorporated herein by reference in its entirety. For other examples of suitable lift assemblies, including their mounting arrangements, reference is made to U.S. Pat. Nos. 7,398,571 and 9,486,373, which are commonly owned by Stryker Corp. of Kalamazoo, Mich. and incorporated herein by reference in their entireties.
Optionally, as noted above, hydraulic circuit 90 may incorporate a hydraulic based logic component that is configured to generate a pilot signal to control another hydraulic component, such as a valve, based on flow through the hydraulic based logic component. In one embodiment, a single hydraulic based logic component, in the form of a flow based pilot valve (194, described below), is employed, but in other embodiments, two or more hydraulic based logic components may be used in series or parallel or a combination of both to achieve the desired logic.
In the illustrated embodiment, hydraulic circuit 90 includes hydraulic circuit 190 that is configured to assist in reducing the pressure on the cap side of the hydraulic cylinder when the hydraulic cylinder is being retracted rapidly, especially when the hydraulic cylinder is not loaded, e.g. when the base is not supporting the patient handling apparatus on a floor or ground surface.
Referring to
Referring again to
For example, hydraulic cylinder 80 typically has a 2:1 rod differential, so that the flow out of the cap end chamber is about twice that of the rate of fluid flow into the rod end chamber. Therefore, when you want to retract the rod at a rapid rate, the rate of fluid flow out of the cap end, which is double the rod end rate, can create some back pressure on the cylinder and/or increased pressure on the pump, which can limit the speed of the rod. Therefore, by redirecting some of the fluid to reservoir R, the pressure on the cylinder and/or the pump can be reduced and, hence, the speed of the rod can be increased without the stress normally associated with such a rapid retract. Thus, instead of being cycled through the pump, the fluid may be able to go straight to the reservoir, which provides a faster path (path of lower resistance) to achieve the circuit completion. In the illustrated embodiment, the switching is “hydraulic switching” and may be all internal to the hydraulics using the flow in the hydraulic circuit and through the hydraulic based logic component, such as the flow based pilot valve described herein. Optionally, this hydraulic switching may be combined with control system logic based on input from a sensor, such as a weight sensor or position sensor (either internal or external), such as described in copending application entitled HYDRAULIC CIRCUIT FOR A PATIENT HANDLING APPARATUS, attorney docket no. 143667.185016 (P-619), filed on even date herewith by Stryker Corp., Which is incorporated by reference herein in its entirety.
Referring again to
First chamber 198 includes a first inlet 202, a second inlet 204, an outlet 206, and a pilot piston assembly 208 mounted for movement in the first chamber 198 between a closed position (e.g.
The pilot piston assembly 208 includes a pilot piston 210 with a piston side 210a (
Second inlet 204 is in fluid communication with the first chamber 198 and outlet 206 of the first chamber 198 regardless of the position of the piston assembly 208 so that fluid flows from the outlet 206 of the first chamber 198 during all fluid flow conditions—during low flow conditions and high flow conditions. In this manner, hydraulic fluid flows through the pilot operated control valve assembly 192 during all flow conditions.
Rapid retraction of rod 212 may be desirable as noted above, for example, when the base of patient handling apparatus 10 is unsupported, and when the patient handling apparatus 10 is being loaded into an emergency vehicle.
Second chamber 200 includes an inlet 220, an outlet 222, for example, formed by a low pressure bypass (LB) orifice, which is in fluid communication with reservoir R, and a valve poppet 224. Inlet 220 of second chamber 200 is in fluid communication with a conduit 230 (
Valve poppet 224 is movably mounted in the second chamber between a closed position (shown in
When the fluid flow to the first inlet 202 of the first chamber 198 exceeds a preselected flow rate, back pressure at the inlet 202 of the first chamber 198 will move the pilot piston 210 from its closed position to an open position (shown in dashed lines in
In the illustrated embodiment, referring again to
Thus, pilot valve 194 provides a flow base pilot valve to control the opening or closing of pilot operated valve 190a, which redirects some of the fluid from the cap end of the hydraulic cylinder 80 to the reservoir and thereby reduces the pressure in the hydraulic circuit (e.g. and its components) and the pump and, further, enables the speed of the rod to be increased.
For example, when the cot is not loaded and the operator wishes to speed up the retraction of the base (for example, when the frame is supported by the deck of an emergency vehicle as described in the above), the higher flow of the fluid through Dow based pilot valve, may cause flow based pilot valve 194 to generate the pilot signal 194a (caused by movement of the valve poppet 224 described above) will open pilot operated valve 190a of pilot operated control valve assembly 192 to allow fluid from the cap side of cylinder 84 to go straight to the reservoir (
In another example, when the cot is loaded with a patient and the operator wishes to lift the frame, the motor will have to drive the pump at a higher speed than when unloaded due to the force need to lift the frame. Flow based pilot valve 194 may be configured to generate the pilot signal when simply raising the frame when it is loaded with a patient (or when a patient has a certain threshold weight) and thereby open the pilot operate valve 190a to reduce pressure on the cap side of the cylinder and the pump due to the increase discharge from the cap side of the cylinder. It should be understood that the threshold valve that triggers the pilot signal may be varied and is controlled by the spring constant of spring 216.
As noted, the pilot signal may be generated at high flow conditions, for example, flow rates that are used for a rapid retraction of rod 212, or for increased rates associated with raising the frame when the apparatus is loaded with a patient. For an ambulance cot designed to carry an adult person and that uses a single cylinder to raise or lower the frame (or retract or lower the base), an example of a low flow rate on the rod side may include a rate in a range of about 0.5 to 1.3 liters/min (l/m) or in a range of about 0.70 to 1.0 liters/minute or in a range of about 0.80 to 0.90 liters/minute. Similarly for an ambulance cot designed to carry an adult person and that uses a single cylinder to raise or lower the frame (or retract or lower the base), an example of a high flow rate on the rod side may include a rate in a range of about 2.0 to 3.0 liters/min (l/m) or in a range of about 2.3 to 2.7 liters/minute or in a range of about 2.40 to 2.6 liters/minute. For the cap side, the flow rate ranges would be approximately double that of the rod side.
Although described in the context of a hydraulic control system for a patient support apparatus, the hydraulic based logic component may be used in other applications and to provide logic for other pilot controlled hydraulic devices to achieve the desired logic in a variety of hydraulic systems.
The terms “head-end” and “foot-end” used herein are location reference terms and are used broadly to refer to the location of the cot that is closer to the portion of the cot that supports a head of a person and the portion of the cot that supports the feet of a person, respectively, and should not be construed to mean the very ends or distal ends of the cot.
While several forms of the cot and hydraulic circuit have been shown and described, other forms will now be apparent to those skilled in the art. For example, one or more of the features of the cot 10 may be incorporated into other cots. Similarly, other features form other cots may be incorporated into cot 10. Examples of other cots that may incorporate one or more of the features described herein or which have features that may be incorporated herein are described in U.S. Pat. Nos. 7,100,224; 5,537,700; 6,701,545; 6,526,611; 6,389,623; and 4,767,148, and U.S. Publication Nos. 2005/0241063 and 2006/0075558, which are all incorporated by reference herein in their entireties. Therefore, it will be understood that the embodiments shown in the drawings and described above are merely for illustrative purposes, and are not intended to limit the scope of the invention, which is defined by the claims which follow as interpreted under the principles of patent law including the doctrine of equivalents.
This application claims the benefit of U.S. Prov. Appl. Ser. No. 62/926,711, filed on Oct. 28, 2019 and entitled HYDRAULIC VALVE AND SYSTEM and is related to U.S. Prov. Appl. Ser. No. 62/488,444, filed on Apr. 21, 2017, entitled PATIENT HANDLING APPARATUS WITH HYDRAULIC CONTROL SYSTEM, by Applicant Stryker Corporation, which are hereby incorporated by reference in their entireties.
Number | Date | Country | |
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62926711 | Oct 2019 | US |