US3036435A - Portable builder's hoist - Google Patents

Description

May 29, 1962 M. SAMUELY PORTABLE BUILDER'S HOIST Original Filed April 25, 1955 5 Sheet l FIG.|.

FIG.3.

MAX SAMUELY INVENTOR HERZIG a JESSUP,

BY ATTORNEYS.

y 2 M. SAMUELY 3,036,435

I PORTABLE BUILDER'S HOIST Original Filed April 25, 1955 3 Sheets-Sheet 2 F l G. 5. F l G. 6. BLOCKED FLOW VALVED CRACKED IIIIIIIII lanmlimnmnw HYD. VALVE HYD. VALVE FU LL FLOW MAX SAMUELY INVENTOR.

HERZIG at JESSUP,

ATTORNEYS.

y 9, 1962 M. SAMUELY 3,036,435

I PORTABLE BUILDER'S HOIST Original Filed April 25, 1955 3 SheetsSheet 5 FIG. nQ

MAX SAM UELY IN VEN TOR.

HER-ZlG JESSU P,

ATTO RN EYS.

Unite rates atent O 3,036,435 PORTABLE BUILDERS HOIST Max Samuely, Los Angeles, Calif., assignor to Tubular Structures Corporation of America, Los Angeles, Calif., a corporation of California Original application Apr. 25, 1955, Ser. No. 503,681, now Patent No. 2,869,325, dated Jan. 20, 1959. Divided and this application Jan. 19, 1959, Ser. No. 787,512

12 Claims. (Cl. 60-53) The present invention relates generally to hoisting equipment and elevators and more particularly to a portable hoist adapted for lifting and lowering materials in the course of constructing or razing buildings. It will be realized from the description to follow that the invention herein described is not limited to the specific embodiments shown and described, but will have application in other allied fields.

This application is a division of earlier filed application Serial No. 503,681, filed April 25, 1955, now Patent No. 2,869,325.

Devices of the type generally described above have been available in the past but have been subject to a number of disadvantages. Previously known hoists of this general type consist of a tower having vertical guides, a platform engaged with the guides, and a simple winch for raising or lowering the platform along the guides.

Prior to the present invention, portable hoists in general use have not been designed for rapid and eflicient use in that they have not incorporated means for accelerating and decelerating the platform travel at the beginning and ends respectively of its movement up and down the tower guides. Because of the lack of such accelerating and decelerating means, the platform movement has been re stricted to relatively slow speeds since the shock attendant to starting and stopping a platform at higher speed involves the risk of breakage of the winch cable or other portions of the hoisting mechanism with obvious disastrous results. Furthermore, it is desirable in hoisting plaster, mortar and other materials carried in the skips that an operator ride on the platform with the material so as to be available to stop the platform at the desired point and roll the skip off the platform at the elevated station. Abrupt stopping and starting of the platform involves severe discomfort and danger to personnel riding thereon and thus should be avoided.

Since the shocks above mentioned has been avoided in the past only by slowing down the platform movement, previous hoists have been somewhat ineflicient, particularly when used for relatively high lifts in the construction of multistory buildings due to the excessive time taken for the platform to travel from the ground to the desired elevation.

Another difficulty encountered in hoists of the type described which have been available heretofore is the fact that the down-travel of the platform has been controlled solely by a mechanical friction brake which tends to become overheated upon continued use particularly in demolition and razing operations wherein the platform is loaded during the down-travel. Mechanical brakes of the type described have the additional disadvantage that they are subject to grabbing or seizure such as to impose excessive shock loads on the hoisting cable running substantial risks of breakage.

Still another disadvantage of prior devices is the fact that no satisfactory means have been provided hereto-fore in hoists of the class described for accurately and automatically positioning the platform at a desired elevated station while at the same time permitting relatively high speed travel during the major portion of the up-travel.

Bearing in mind the foregoing difiiculties, it is a major object of the present invention to provide a portable hoist ice of the class described in which relatively high speeds of up and down travel may be obtained without attendant shocks at the beginning and end of such travel.

It is another object of the present invention to provide portable hoisting equipment of the class described in which the speed of up and down travel may be adjusted over a relatively wide range for various applications.

It is still another object of the invention to provide hoisting equipment of the class described which is capable of accurate and automatic placement of the hoisting platform at a desired elevated station.

It is a further object of the invention to provide equipment of the class described wherein a high speed of platform travel is combined with an automatic decelerating means which slows the platform down just prior to reaching the desired elevated station.

An additional object of the invention is to provide for fully controlled down-travel of platform in hoisting equipment of the class described Without the use of mechanical friction devices.

Yet another object of the invention is to provide hoisting equipment of the class described wherein the speed and operation of the power prime mover is automatically coordinated with motion of the platform.

Yet a further object of the invention is to provide an automatic safety brake system for stopping the downtravel of the platform in the event of failure of the speed control equipment.

Another object is to provide improved and simplified hydraulic circuitry in a hydraulic hoist wherein the hoist drives a motor-pump unit acting as a pump during down movement.

Another object is to provide an improvement as in the foregoing wherein automatic flow restrictors are provided in the hydraulic connection to the motor-pump unit so as to control the up and down travel of the hoist.

Another object is to provide in the system an internal composition prime-mover controlled by a hydraulic throttle and a hydraulic brake having simplified hydraulic circuitry for providing automatic actuation of the throttle and brake.

The foregoing and additional objects and advantages of the invention will be apparent from the detailed description to follow, consideration being given to the ac companying drawings in which:

FIG. 1 is an elevational view of a portable builders hoist embodying the present invention, the same being shown in a. lowered or traveling position;

FIG. 2 is a fragmentary side elevational view of the hoist shown in FIG. 1 in erected positions ready for operation;

FIG. 2a is an enlarged horizontal section taken on the line 2a-2a of FIG. 2;

FIG. 3 is a fragmentary elevational view partially sec, tioned, showing a first form of hydraulic control valve and operating cam embodied in the hoist shown in FIGS. 1 and 2;

FIG. 4 is an elevational section taken on the line 44 in FIG. 3;

FIGS. 5, 6, and 7 are sequential semi-schematic views of a second form of hydraulic control valve and operating cam which may be embodied in the hoisting equipment shown in FIGS. 1 and 2;

FIG. 8 is an axial section of a uni-directional, constant flow regulator incorporated in various of the control systems embodied in the present invention;

FIGS. 9, 10 and 11 are hydraulic circuit diagrams schematically illustrating the operation of certain forms of the invention during the up-travel, stop, and downtravel conditions respectively;

FIGS. 12 and 13 are fragmentary semi-schematic views of aprime mover throttle control portion of the system shown in FIGS. through 12 showing respectively, open and closed throttle positions.

The portable builders hoist embodying the present invention is indicated 'in'the drawings generally by the reference character and comprises a frame-work tower 31 having longitudinal guide rails 32 on a forward face thereof, a load carrying platform33 mounted for sliding movement along the rails 32 and a draw works 34 incorporating a winch drum 35 having a hoisting cable 36 reeved through conventional sheave means shown generally at 37 whereby to hoist or lower the platform 33. The hoist 36 includes a base frame 40 having suitable ground engaging pads 41 and 42, the entire structure being mounted on a pair of trailer wheels 43 whereby the hoist 30 may be drawn behind a towing vehicle being attached by conventional trailer attachment means (not shown) at the upperend 44 of the tower 31.

When it is desired to lower the tower 31 from the operative position shown in FIG. 2 to the traveling position shown in FIG. 1 the rearmost ground engaging pads 42 are retracted lowering the wheels 43 to the ground and the tower 31 is thereafter tilted rearwardly (counterclockwise in FIG. 2) about a horizontal pivot axis at 45 until the tower rests against abutments 46 connected to the carriage (not shown) supporting the wheels 43.

Power to operate the hoist 30 is derived from a prime mover 50, inthe present case an internal combustion engine. As may be seen in FIGS. 9 through 11, the prime mover 50 is mechanically connected to drive a hydraulic pump 51 which may be any type of relatively high pressure pump preferably of the positive displacement type such as a gear pump, vane pump or the like. The pump 51 derives its fluidfrom a storage tank 52 and delivers it through control means to be determined in more detail later herein to a hydraulic motor 53 which is again preferably of the positive displacement type. The hydraulicmotor53 is mechanically connected todrive to unwind from the drum 35 and this unwinding rotation of the drum 35 in turn driving the motor 53 backwardly causing the same to pump fluid. The speed of the down travel of the platform 33 may therefore be controlled by restricting the flow from the hydraulic motor 53 (now acting as a pump).

Restriction to flow from the hydraulic motor 53 during the down-travel of the platform 33 is effected by an adjustable flow regulator 63 (see FIGS. 9-11) which in the first form of invention takes the form of a uni-directional flow regulator, the construction of which is shown in FIG. 8. In the device shown in FIG. 8 flow regulation takes place only when the flow is from the motor 53, i.e., through the device in a direction entering at the conduit 69 and leaving at the conduit 70. This flow direction is indicated by the arrow in the conduit 69 in FIG. 8 and it will be seen that as the fluid passes in this direction into a chamber 71 in the regulator 63 a restricted orifice 72 in a slideable piston valve member 73 therein, causes pressureto build up in the chamber 71 urging the piston 73 to the left against the yielding resistance of a spring 74. The resistance of the spring 74 may be adjusted by an abutment screw 75 by which the initial stress on the spring 74 may be varied. As the piston 73 moves to the left, the skirt thereof passes across an exit port 77 leading to the conduit wand thus causes an additional restriction to flow through the entire regulator 68. For any given pressure, the increased restriction at the port 77 decreases the winch drum 35 to wind the cable 36 thereon and lift the platform 33.

A spring-held pressure suspended friction brake 55 is operatively associated with the winch drum 35 and fluidconnected to the hydraulic system whereby the drum 35.

is held stationary by a brake shoe 56 forced into contact therewith by the compression spring 5 7 except where there is operative hydraulic pressure in a high pressure conduit 58 as will be described. Pressure in the conduit 58 forces fluid into the upper end of an actuating cylinder 59 causing a piston 60 to draw downwardly on the brake shoe 56 releasing the same from the 'drurn35 and permitting the latter to rotate. The compressive force 'of the spring 57 is Is'ufiicient to hold the drum 35 stationary with the platform 33 in a raised position and with the maximum permissible load thereon. The brake 55 is used only to lock the platform in a desired position and is not'used to slow the down-travel of the platform 33; 'Other means are provided for the latter purpose as s will be explained.

The hydraulic pressure system also includes a conduit 62 leading to an actuating cylinder 63 having a piston 64 therein mechanically connected to a throttle lever- 65 which controls the speed of the prime mover 50. A compression spring 66' normally urges the throttle lever 65 upwardly, iJe. in a closed throttle direction... The open throttle and closed fthrottle conditions are illustrated in FIGS." .12 and 1-3 respectively. From the foregoing it 50 and the same idles. When pressurized fluid is introduced through'the conduit 62 into the actuating cylinder 63, however, the piston 64 moves downwardly opening the throttleand speeding up the operation of the prime mover 50 thus increasing the power delivered to the pump 51.

the rate of flow through the regulator 68. As such flow must all pass through the orifice 72 the decrease in rate of flow decreases the pressure in the chamber 71 thus permitting the spring 74 to move the piston 73 to the right tending to open the port 77. When these two opposing forces reach a condition of equilibrium the rate of fluid flow through the regulator 68 reaches a certain relatively constant value and it will be seen that this value is substantially the same irrespective of the pressure at the con duit 69. 7

Thus the maximum speed at which the motor 53 may be driven by the drum 35 during the down-travel of the platform -33 is limited to that which produces the limited flow rate through the regulator 68.

In order to prevent damage to the pump 51 or the hydraulic'motor 53 in the event of a malfunction in the control system causing abnormal flow through these devices, each is connected by a high pressure relief valve to the storage tank 52. The high pressure relief valve for the pump 51 is indicated in the drawings at. 80 and that for the hydraulic motor 53 is indicated at 81;

As thus far described, it will be seen that the control of the platform '33 whereby it is caused to move upwardly or downwardly as desired is accomplished by connecting the pump 51 to deliver pressure to the hydraulic motor on the one hand or alternatively connecting the output of the motor 53 to the tank 52 through the flow regulator 68 in such manner as to restrict the fluid flowing from the hydraulic motor 53. These selective connections are accomplished by means of a master control valve 85 which in the form illustrated in FIG. 3, is a four-way three position spool valve.

The internal construction of the'valve 85 is more or less conventional and is illustrated in FIG. 3 wherein it will be seen that pressure fluid introduced at a conduit 86 will be seen that when there-is no pressure inthe conduit .62 the spring 66 closes the throttle of the prime movermay be selectively connected through internal passages in the valve to a tank connection conduit 87; a motor connection conduit 70, or an alternate return conduit 88. Selective inter-connection as just described is accornplished by moving a spool member 89 axially within the body of the .valve 85 in one direction or the other from a central position inwhich itis held bya centering spring assembly illustrated at 99;

' Inasmuch as the specific details of the four-way valve employed in the present invention are conventional and inasmuch as the invention does'not' reside in the particular design of the valve itself, no further detailed description is deemed necessary herein. Sufiice it to say, that when the spool 89 is moved to its right-hand limiting position (e.g. FIG. 9) pressure fluid from the conduit 86 is connected to the conduit 70. When the spool 89 is centered (e.g. FIG. 10) fluid from the conduit 86 may flow unrestricted through conduit *87 to the tank 52.

Interposed in the return conduit 88 between the control valve 85 and the tank 52, is a flow restriction valve relief 95, the purpose of which is to maintain some pressure in the conduit 58 even when the valve is in position to return pressure fluid through the conduit 83 to the tank 52. This pressure in the system is required during downtravel as can be seen in FIG. 11, in order to hold the brake-shoe 56 away from the drum 35 and permit downtravel of the platform 33 and also to maintain pressure in the conduit 62 so as to open the throttle of the prime mover 50 sufiiciently to produce the pressure necessary to hold the brake off.

At this point it should be noted that the system fails safe that is, in the event of a failure of the prime mover or any part of the hydraulic system, pressure is released from the brake actuating cylinder 59 or never builds up therein, thus keeping the brake on and preventing operation of the system until the failure is corrected.

Movement of the spool 89' back and forth from its spring centered position in the body of the valve 85 is effected by a rotary cam system mounted on a shaft 96 and adapted to engage one or the other of two cam follower rollers 97 and 98 which are in turn mounted on a common slide member 99 connected through a connecting rod 100 to the spool 89.

In one form of the device illustrated in full line in FIG. 3, a finger-like cam 101 (shown in full line in FIGS. 9-11) is employed, having a relatively restricted cam surface 102 adapted to contact the rollers 97 and 98 only at, or near the ends of its 180 rotary movement. In this form, a dash-pot 102 is operatively associated with the connecting rod 100 whereby to damp the motion of the spool 89 returning to its center position from either of its left-hand or right-hand limited positions. That is, assuming the cam 101 to have been rotated to its lirni-ting position clockwise thus contacting the cam follower roller 98 and moving the spool 89 to its extreme righthand position and assuming that the cam 101 is thereafter rotated to a centralized position as illustrated in full line in FIG. 3, the spool 89 will return to its central position under the urging of the centering spring assembly 90. The spool will however return somewhat slowly due to the damping action of the dash-pot 102 wherein a piston 103 causes fluid on one side thereof to pass through a restrictive orifice 104 and a passage 105 to the other side of the piston 103. The restriction of the orifice 104 may be adjusted by a needle valve 106. The purpose of this arrangement will be described later herein,

As can be seen in FIG. 2, the cam shaft 96 is mounted on a common base with the winch-drum 35 and prime mover 50 is drivingly connected through sprocket chains 110 and 111 to a control cable drum 112. Two sprocket chains 110 and 111 are employed and engage separate sprockets on a common shaft coaxial with the Pivot axis at 45 whereby the raising and lowering of the tower 31 does not interfere with or disturb the driving connection between the cam shaft and the cable control drum 112.

Provision for manual, as well as automatic operation of the master control valve 85 is made in the form of a control cable 115 mounted on a pair of drums or pulleys the lower one of which is the control drum 112 and the upper of which, indicated at 116, is mounted at the upper end of the tower 31 whereby to provide a length of control cable at 117 which is parallel to and closely adjacent the platform guides 32.

Clamped to the cable 115 at appropriate points along the length 117 are two stop members 118 and 119 conventionally referred to as eggs. As can be seen in FIG. 2 the platform 33 is provided at its rearward edge with a pair of vertically extending slide members 120 adapted to engage the guides 32. At the upper end of one of the slide members 120 is a closed fork 121 which is positioned to bracket the cable length 117 as can be seen in FIG. 2A.

It will be seen that as the platform 33 reaches either its upper or lower limiting position in its travel along the tower 31, the fork 121 engages one of the other of the eggs 18 and one 19, thus moving the cable 115 and rotating the control drum 112. The rotary motion of the control drum 112 is transmitted through the previously described sprocket chain connection and cam to the valve spool 89 thus changing the position thereof. The just described control cable-sprocket chain connection to operate the valves is common to all of the invention illustrated herein.

As has been previously described the normal position of the valve spool 89, when not influenced by the cam 101, is in the center of its movement in the body of the valve 85. When in this position as shown in full line in FIG. 3 and as is indicated schematically in FIG. 10, pressure fluid entering at 86 is transmitted directly through the valve without substantial resistance and returned to the tank 52 through return conduit 87. Since there is no resistance to the flow of fluid in the manner just described substantially no pressure is developed in the conduit 58 and thus the brake shoe 56 remains against the drum 35 and the throttle 65 remains in idling position.

The normal or non-operating position of the cam 101 is shown in full line in FIG. 3 wherein it will be seen that the cam is midway between the cam follower 97 and 98 and out of contact with the same.

Operation Assuming that the platform is resting on the ground, has been loaded, and it is now desired to raise the same; the operator pulls downwardlyon the cable length 117 (this motion is possible since the lower egg 118 is below the fork 121). Downward movement of the cable length 117 rotates the control drum 112, and hence the cam shaft 96 in a clockwise direction thus bringing the cam surface 102 against the cam follower 98 and moving the valve spool 89 to its right hand limiting position. This condition is illustrated in FIG. 9 wherein it will be seen that the valve is placed in a position to intercommunicate the pressure conduit 86 with the outlet conduit 70 which communicates through the flow regulator 68 with the hydraulic motor 53. It will be noted that in this condition the flow through the regulator 68 is in the reverse direction (as to the regulator) thus forcing the piston 73 upwardly and permitting the full flow that can pass through the orifice 72. The flow just described delivers pressurized fluid through the conduit 69 to the hydraulic motor 53 whence it is returned through a return conduit 129 to the tank 52. This in turn causes powered rotation of the drum 35 in a direction to lift the platform 33 as previously described.

It will be noted that the pressure in the conduit 58 lifts the brake shoe 56 from the drum 35 and also, through the conduit 62, operates the actuating cylinder 63 to open the throttle 65. It will also be noted that should the hydraulic system fail at any time the pressure in the conduit 58 would drop permitting the spring 57 to engage the brake 55 and hold the platform 33 at its then position along the guides 32. Similarly, such a failure would close the throttle on the prime mover 50 and prevent the same from running away due to a no-load condition.

Returning now to the operation of the platform 33 in an upward direction, let it now be assumed that the fork 121 reaches the upper egg 119 thus rotating the control drum 112 in a counter-clockwise direction and moving the cam 101 from its position against the cam follower 98 to its vertical disengaged position illustrated in FIGS. 3 and 10. Referring to the form of the invention illustrated in FIG. 3 it will be realized that the return of the valve 7 spool 89 to a centralized position under the urging of the spring assembly 90 will be damped or slowed down by the dash-pot mechanism 102 due to the fact that liquid must be forced from the left-hand side of the piston 103 through the restricted orifice 105 to the right-hand side of the piston 103. The just described damped movement of the valve spool 89 gradually cuts off the communication between the pressure conduit 86 and the output conduit 70 so that the fluid delivered to the hydraulic motor 53 is cut off gradually rather than abruptly. It has been found that if the cut-oif is gradual over a period as short as one second or even less, the shock upon stopping the platform is substantially eliminated. On the other hand,

if the valve spool were permitted to snap back to central position under the sole control of the spring assembly 90 the stoppage of the platform 33 is not only unduly abrupt but the shock in the hydraulic fluid system is also severe.

in addition to preventing the sudden stoppage of the platform 33, it will be seen that the dash-pot 102 imposes a yielding resistance to movement of the spool 89 to either of its left-hand or right-hand positions at the time that the cam 101 is manually moved into engagement with the followers 97 or 98. Thus, the operator is prevented from inadvertently jamming the valve 85 into 'full speed condition, imposing an undue starting load on the device. r

In addition to the automatic stopping at the'contact of the fork with the upper egg.119, platform 33 may of course be stopped at any desired position by an operator on the ground lifting on the cable length 117. Also, an

operator riding on the platform 33 can, in the usual manner, stop the platform at any desired point by seizing the cable length 117 and lifting the same or permitting the I is rotated counter-clockwise to the left-hand position against the cam follower 97 moving the valve spool 89 to its left-hand position and intercommunicating the conduit 70 leadingfrom the hydraulic motor 53 with the return conduit 87 connected to the tank 52. At'the same time, the pressure conduit 86 'is connected as shown in FIG. 11, to the output conduit 88 and fluid is delivered through the restrictive valve 95 to the tank 52. The pressure built up in the conduit 58 by-reason of the restriction imposed at the valve 95 is sufficient to release the brake 55 and also to open the throttle 65 through the fluid actuated devices 59 and63 previously described.

The brake 55 having been released, the weight of the platform 33 and any load thereon causes the cable 36"to unwind from the drum 35 which now drives the hydraulic motor causing the same to operate as a pump. The motor 53 then receives fluid through the conduit 12.9 from the tank 52 and' pumps the same through the regulator 68, the conduit70, the valve 85, and the return conduit 87'back to the tank 52. The flow rate through flie regulator 68 maybe adjusted by means of the adjustmerit screw 75 as previously described, and is adjusted to give the desired rate of downward travel of the platform. It will be noted that this downward travel rate is substantially uniform and remains approximately the same irrespective of the load on the platform 33 since the rate of down-travel is directly proportional to the rate of fluid of the effective cam surfacefdwell portions 133and 134' adjacent the rise portions 131 and 132 and a central high dwell at 135. In this form of cam controlno dash-pot is required, the desired graduated operation being accomplished by the cam alone.

The respective positions of the cam 13!) and the valve spool 89 during stopping and starting are shown in FIGS. 5, 6, and 7. It will be seen that when the cam 130 is rotated for example clockwise to engage the follower roller 98, its first contact moves the spool 89 out of its centralized position and for a short time, blocks all flow through the valve 85. The result of this is to quickly build up pressure in the conduit 58, thus releasing the brake 55 and opening the throttle 65 in the manner previously described. The next successive position of the cam 130 and valve spool 89 is illustrated in FIG. 6 wherein it will be seen that upon reaching the dwell 134, for example, the valve 85 is slightly cracked whereby to permit a highly restricted flow of fluid therethrough. The effect of this is to slowly start the motor 53 (either upwar-dly tor downwardly depending on the left-hand or right-hand position of the spool 89) thus preventing an abrupt start. Such slow speed (about /2 normal speed) 7 continues as long as the cam follower 97 or 98 is engaged with the dwell 133 or 134.

When'the cam 130 is now rotated to its limit in either the right-hand or left-hand position, the engaged follower 97 or .98 is lifted onto the high dwell portion 135 whereupon the valve spool 89 is moved to the full open position as illustrated in FIG. 7 causing the platform 33 to move at full speed.

While the forms of the device shown and described herein are fully capable of achieving the objects and providing the advantages hereinbefore stated it -will be realized that they are capable of considerable modification and rearrangement Without departure from the spirit of the invention. For this reason, I do not mean to be limited to the forms shown and described but rather to the scope of the appended claims.

What is claimed is:

1. In a hoist'of the type having a load such as a carrier to be lifted or lowered, a hydraulic motor for lifting said load which motor acts as a pump upon lowering of the load, a hydraulic system including a tank, a pump having an outlet and valve means for reversing the flow of hydraulic fluid through the motor, the improvements comprising: means incorporated in said valve means for freely bypassing fluid from the outlet of the pump through a first passage to the tank when the valve is in load stopping position, said valve means having a down position wherein hydraulic 'tluid from the motor is returned to the tank through a second passage having flow restricting means therein whereby pressure is maintained in the outlet of said pump, and means responsive tosaid pressure for controlling the functioning of portions of said hoist.

2. The structure of claim 1 wherein said last-named means comprises a hydraulic brake of the type having means which are released upon the application of hydraulic pressure thereto, said brake having a direct connection to the outlet of said pump so that the said brake is released whenever there is pressure in said pump outlet.

3. The structure of claim 1 including a prime mover for driving said pump, saidprime mover having a hydraulic throttle of a type which opens upon the application of pressure thereto and having a direct connection to the outlet of said pump so that said throttle is opened wheneverthe outlet of said pump is not freely bypassed to the tank, 7 j

4. The structure of claim 3' including a hydraulic brake of the type having means which are released upon the ing an intermediate position and an up position and cam means for actuating said valve means from its intermediate position to either the up or down position.

6. The structure of claim wherein said cam means includes a cam having a configuration providing for variable degree of opening of the ports in said valve means.

7. In a power hoisting system a hydraulic transmission comprising: a source of pressurized fluid; a reservoir; a hydraulic motor-pump having a port and being connected to drive as a motor when supplied with pressurized fluid at said port and to deliver pressurized fluid at said port when mechanically driven as a pump; conduit means connected between said source of pressurized fluid, reservoir and said port to said motor-pump; valve means interposed in said conduit means having an up position in which the source of pressurized fluid is connected with said port and a down position in which said port of said motor-pump is connected to said reservoir and automatic flow regulator means connected to restrict flow from said motor-pump to regulate its rate of operation when acting as a pump.

8. The structure of claim 7 wherein said flow regulator is of a type which provides for relatively unrestricted flow in the reverse direction so 'as to allow relatively free Iflow of hydraulic fluid to said motor-pump when acting as a motor.

9. The structure of claim 7 including a hydraulically operated brake and brake motor associated with said hoi said brake being of a type arranged to release upon the application of hydraulic pressure to said brake motor, means providing a direct connection from said source of pressurized fluid to said hydraulic brake motor, and flow restricting means providing for restricting the output of said pump in both the up and down positions of said valve means whereby suflicient pressure is developed in said connection to actuate said brake motor.

10. The structure of claim 7 including a prime mover connected to said source of pressurized fluid, said prime mover having a hydraulically operated throttle having a connection to said source of pressurized fluid whereby said throttle is moved whenever the output of said source of pressurized fluid is restricted so as to increase the pressure in said connection.

11. The structure of claim 9 including a first unrestricted bypass passageway from said valve means to said reservoir and a second restricted passageway from said valve means to said reservoir, said valve means including means whereby said restricted passageway is open for communication with said valve means in the down position of said valve means.

12. The structure of claim 9 including a uni-directional flow regulator connected between said valve means and said motor-pump adapted to offer restriction to flow from said motor-pump but to allow free flow of hydraulic fluid thereto.

References Cited in the file of this patent UNITED STATES PATENTS 1,259,090 Ferris et al. Mar. 12, 1918 2,316,926 Willett Apr. 20, 1943 2,321,880 Vickers June 15, 1943 2,399,685 McCoy May 7, 1946 2,407,692 Vickers Sept. 17, 1946 2,416,801 Robinson Mar. 4, 1947 2,545,440 Barber Mar. 20, 1951 2,599,052 Forman June 3, 1952 2,681,117 Marcy June 15, 1954 2,789,542 Vander Kay Apr. 23, 1957 2,869,325 Samuely Ian. 20, 1959

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