US2352736A - Automatic resetting device for governors - Google Patents

Description

July 4, 1944. N. R. RICHMQND 2,352,736

" l AAUTOMATIC, RESETTING' DEVICE FOR GOVERNORS Filed octf. 2. 1940 Patented July 4, 1944 Amirri-:D

STATES rATEN'r OFFICE AUTOMATIC RESETTING DEVICE FOR GOVEBINORS Nelson R.'.Biclimond, Thompsonville. Conn., as-

signor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Application october z, 1940, serial No. 359,370

4 claims. `(ci. 264-3) tions under which the manual setting device does not provide adequate control and for returning the governor to the manual setting when such special operating conditions terminate.

A somewhat more specic object resides in the provision in a governor for a controllablepitch propeller of means for automatically resetting the governor for propeller speeds below a predetermined minimum to prevent the propeller from attaining a speed materially above the speed for which the governoris normally set as the speed of the propeller is increased.

Other objects [and advantages will be more particularly pointed out hereinafter or will become apparent as the description proceeds.

In the accompanying drawing, in which like reference numerals areused to designate similar parts throughout, there is illustrated a suitable mechanical embodiment for the purpose or disclosing thel invention. The drawing, however, is for the purpose of illustration only and is not to be taken as limiting or restricting the 1nvention since it will be apparent to those skilled in the art that various vchanges in the illustrated construction may be resorted to without in any way exceeding the scope of the invention, as deilned by the claims.

In the drawing, Fig.4 1 is a longitudinal sectional view through a governor constructed according to the invention. and

Fig. 2 is a schematic sectional view showingA the governor applied to control the pitch of a controllable-pitch propeller. y

Referring tothe drawing in detail, the numeral Il 'generally indicates the speed governor andthe numeral l2 generally indicates a controllable-pitch propeller the pitch of which is regulated by the action of the governor III. In the illustrated arrangement the governor actuates a valve for controlling the pitch .of a hydrocontrollable feathering-type propeller one illustrative form of which is clearly illustrated and described in United States Patent No. 2,174,717, issued October 3, 1939, to Frank W. Caldwell et al., for Multiposition controllable pitchpropeller. *l

`pressure required to operate the propeller.

It is well known to operate a controllablepitch propeller under governor control tov estab- 4lish a substantially constant engine speed by changing the propeller pitch to vary the load on the engine whenever the engine tends to speed up or slow down. It is also well known to manually adjust the governor setting so that the propeller will maintain the engine speed substantially constant at a selected rate.

. In the nhydro-controllable propeller and control system illustrated in Fig. 2, hydraulic uid.

such as engine lubricating oil at lubricating oil pressure, is supplied through the channel I4 to the intake of a booster pump I6. The outlet of the pump is connected with a pressure chamber I 8 one end of which leads into a valve bore 2l and the other end of which leads to a pressure relief valve 22 which is operative to maintain a predetermined uid pressure in the chamber I8 cr to maintain the huid pressure in the chamber I 8 a predetermined amount above the fluid A valve plunger 24 is slidable in the bore 20 and controls the ports 26 and 2B in such a manner that the propeller line 30 may be connected with the pressure chamber I8 or may be vented to drain through the hollow plunger 24 and the lower end -of the bore 20. At its upper end the plunger 24 is operatively connected to a speed governor having centrifugally actuated flyballs 32 opposed by a speeder spring 3G.' The upper end of the speeder spring rests against the lower` end of a movable abutment 36 which is adjustable to various positions by the manually actuatable mechanism including the pulley 38 and pinion 40' the teeth of which mesh with rack teeth provided on one side of the movable abutment. By rotating the pulley 38 the lowermost operative position of the abutment 36 and the load on the speeder spring 34 can be changed to change the speed setting of the governor. 'If

desired the propeller I2 may be of the feathering type and the unfeathering operations may be controlled by the high pressure pump 42 connected to the propeller line 30 through the pressure operated cut-oi! valve 44 which acts to cut-oil' the connection 46 between the` governor operated valve and the propeller whenever the high pressure pump 42 is operated and simultaneously connect the outlet of the high pressure-pump directly with the propeller line 20.

The governor setting mechanism may be adjusted for a selected engine speed land will then maintain the engine at. or nearthe selected ss speed by varying propeller pitch as long uthe engine develops sumcient power to rotate the propeller at the selected speed. If, however, the engine is brought to an idling condition for some particular maneuver, such as a. dive or a landing glide, it will not develop suiiicient power to maintain the speed for which the governor is set. The governor will then change the propeller pitch setting in an attempt to reduce the engine load suiliciently to maintain the selected speed and will maintain the propeller in this ilat pitch condition as long as the engine power remains insuihcient to rotate the propeller at the selected speed. If, with the engine at reduced power and the propeller in its iiat pitch condition, the engine power is increased, the propeller pitch will not be changed until the engine speed begins to exceed the speed for which the governor is set. As soon as the selected speed is reached the governor will immediately begin to function to increase the propeller pitch and increase the load on the engine to maintain the selected speed. However. as an appreciable time interval is required for the governor to change the propeller pitch from the at or extreme low pitch condition to a pitch angle suflicient to slow down the engine, during this interval the engine speed may go considerably beyond the speed for which the governor is set and, if the engine power is increased rapidly, this overshootlng or overspeed ing of the propeller may reach dangerous proportions before the governor control can increase the propeller pitch a suicient amount to slowdown the engine. It is among the objects of the present invention to incorporate into'a propeller speed control device of the character indicated suitable ineans for preventing this overspeeding of the propeller incident to a rapid increase in engine power from a power value below that necessary to drive the propeller at the speed for which the speed controlling governor is set and one illustrative form of such a device is particularly shown in Fig. 1.

The abutment 36 is formed in two parts, as indicated at 48 and 50. Of these the outer part 48 is in the form f a sleeve slidable in the bore of the cylinder 52 formed on the governor cap 54 immediately over the upper end of the spring 34. This sleeve has rack teeth 55 along one side thereof meshing with the teeth of the adjusting pinion 40 and is provided at its lower end with a stop in the form of an internal ange or inset 58. A piston 60 is slidable in the sleeve 48 and in the upper reduced portion of the bore .of the cylinder 52 and carries in its lower end an adjustable spring seat i2.

connected oil chamber 4i to the space at the closed end o! the cylinder '52 on top of the piston 8l so that oil at propeller oil pressure is supplied to the cylinder to urge the piston il downwardly relative to the sleeve 48 against the stop no uid pressure will be lpresent in the chamber 48 and under these circumstances the piston 8l may rise to relieve the load on the governor speeder spring 34.

Assuming that the engine power has been duced so that the engine is no longer able to rotate the propeller at the speed for which the governor is manually set and that, in its eiIort to relieve .the engine 1o`ad andv maintain the selected speed, the governor has maintained the plunger 24 in a position to vent the propeller line through the port 26 until no pressure is left in the propeller line and the chamber 46, the piston 60 will then rise in the cylinder 52 and leave the stop 58 at the same time relieving the loaden the speeder spring 34 and setting the governor for a much lower speed than that for which it was set by the manual control. For instance we might assume that the manual adjustment is set for 2,000 revolutions per minute and when the piston 60 is at the closed end of the cylinder l chamber I8 and as soon as the speed has reached 1,000 R. P. M. the governor will act to connect the ports I28 and 26 to admit oil to the propeller pitch changing mechanism through passages 48 and 30 to start increasing the propeller pitch. As the oil pressure in the propellerline 3l builds up, this pressure will be transmitted through conduit 84 tothe top of the piston 60 and will begin to change the governor setting. We will thus have a condition in which the propeller' pitch is being increased to retard the engine speed and the governor setting is being changed toward a higher speed setting at -the same time. With properly proportioned parts and iiuid connections the piston will reach the stop 58 at somewhere near the same time that the engine speed reaches the speed at which the governor is set. Since the propeller mechanism is full of oil at this time and l the propeller pitch has already been increased to bring the engine and propeller speeds under control of the governor at the gradually increasing speed setting, when the engine and propeller set with substantialLv no overspeeding of the p ro- Y peller at this period. As long as the power developed by the engine is sumcient to drive the.

propeller at the speed for which the governor is set there will be suillcient oil pressure on top of the piston 68 to maintain the piston in contact with the stop 58 and the speed settingof the governor will remain that at which the governor is set by the manual adjusting mechanism.

While a particular mechanical arrangement has been hereinabove described and illmtnted in theaccompanying drawingiorthepurposeofdis closing the invention, it is to be understood that the invention is not limited to the particular construction so illustrated and described, butthat -such changes in the size, shape and arrangement' of the various parts maybe resortedto as come within the scope of the sub-joined claims.

Having now described the invention so that othersskilledintheartmayclearlyunderstand thesamewhatitisdesiredtosecurebyletterl Patent is as follows:

1. In a governor having a speeder spring and blades are against the low pitch limit stop that?! havingavalvefor admittinghydrauliciiuidtoan assenso 3 apparatus to be governed, a two part spring abutment for adjusting the speeder spring, mechaniactuated means 4being connected with the supply line between sad valve and said apparatus so that when said valve is moved to admit fluid to said apparatus, iiuid is admitted to said hydraulic means. y

2L In a governor for controlling amechanism by. controlling the'application of hydraulic flud under pressure to said mechanismy and having a speeder spring, speeder spring setting means having a low speed position and a high speed position, said means including hydraulically actuated means movable by the pressure of hydraulic iluid to compress said spring and move said setting means to high speed position, said setting means being movable to said low speed position by said governor speeder spring upon failure of thehydraulic pressure in said hydraulically actuated means, an abutment against which said setting means is movable by said hydraulic iluid and constituting a stop for determining the high speed position of said setting means and manual means for adjusting said abutment.

3. A governor speeder spring adjusting means' comprising a governor valve movable by said spring and controlling fluid under pressure, means for conducting iluid controlled by said valve from said valve to mechanism to be governed, a iiuid operated device for compressing said spring and a mechanically actuated device for limiting the extent of compression of said spring by said iiuid operated device, a uid conduit connecting said iluid operated device and said valve to conduct a portion of said controlled fluid to said fluid operated device to operate said iiuid operated device and compress said spring.

4. In a speed governor in combination means. for setting said governor to maintain selected speeds comprising means for adjusting a stop, means for adjusting the governor speed setting, means for holding said speed setting adjusting means against said stop to determine a selected speed setting, means rendered operative by a sus-'- tained governor speed below said selected speed to disable said holding means and change the governor speed setting to a lower speed value, and

means, including means responsive to governor speed, for energizing said holding means and restoring said selected speed setting when the governor speed exceeds said lower speed value.

NELSON R. RICHMOND.

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