Controls for power drive assemblies

A power drive assembly and control therefor comprising a primary energy source, a hydrostatic pump driven by said energy source, a consumer of hydrostatic energy connected to and receiving fluid under pressure from said pump, a multiway valve between the pump consumer for controlling the flow therebetween, said multiway valve providing a throttling effect in its intermediate position, a control pressure dependent valve having a first control pressure chamber connected between the pump and multiway valve and a second spring biased control chamber connected between the consumer and multiway valve whereby the first control chamber acted upon by the pressure in front of the multiway valve and the second control chamber is acted upon by pressure beyond the mulltiway valve, a fluid passsage in said valve controlled by differential pressure in said first and second chambers, said passage connecting a control pressure inlet and outlet, a source of control pressure connected to said control pressure inlet, a control cylinder connected to the control pressure outlet, biasing spring in said control cylinder acting in opposition to control fluid delivered from said control pressure dependent valve, an adjusting element on the primary energy source and a connection between said adjusting element and a moving element of the control cylinder on the side opposite the connection with the control pressure valve and wherein pressure dependent reversing valve is connected between a parallel connection formed from a control pressure line of another drive and the multiway valve and the second chamber of the pressure dependent valve.

A power drive asssembly and control therefor comprising a primary energy source, a hydrostatic pump driven by said energy source, a consumer of hydrostatic energy connected to and receiving fluid under pressure from said pump, a multiway valve between the pump and consumer for controlling the flow therebetween, said multiway valve providing a throttling effect in its intermediate position, a control pressure dependent valve having a first control pressure chamber connected between the pump and multiway valve and a second spring biased control chamber connected between the consumer and multiway valve whereby the first control chamber acted upon by the pressure in front of the multiway valve and the second control chamber is acted upon by pressure beyond the multiway valve, a fluid passage in said valve controlled by differential pressure in said first and second chambers, said passage connecting a control pressure inlet and outlet, a source of control pressure connected to said control pressure inlet, a control cylinder connected to the control pressure outlet, a biasing spring in said control cylinder acting in opposition to control fluid delivered from said control pressure dependent valve, an adjusting element on the primary energy source and a connection between said adjusting element and a moving element of the control cylinder on the side opposite the connection with the control pressure valve and wherein a pressure dependent reversing two way valve is provided having one inlet receiving fluid from the pressure dependent valve and delivering fluid to the operating cylinder, a hydrostatic transmission drive and a second inlet connected to a control pressure line which determines the setting of the hydrostatic power transmission drive unit.

A power drive assembly and control therefor comprising a primary energy source, a constant displacement hydrostatic pump driven by said energy source, a consumer of hydrostatic energy connected to and receiving fluid under pressure from said pump, a multiway valve between the pump and consumer for controlling the flow therebetween, said multiway valve providing a throttling effect in its intermediate position, a control pressure dependent valve having a first control pressure chamber connected between the pump and multiway valve and a second spring biased control chamber connected between the consumer and multiay valve whereby the first control chamber is acted upon by the pressure in front of the multiway valve and the second control chamber is acted upon by pressure beyond the multiway valve, a fluid passage in said valve controlled by differential pressure in said first and second chambers, said passage connecting a control pressure inlet and outlet, an auxiliary constant displacement pump supplying control pressure connected to said control pressure inlet, a control cylinder connected to the control pressure outlet, a biasing spring in said control cylinder acting in opposition to control fluid delivered from said control pressure dependent valve, an adjusting element on the primary energy source and a connection between said adjusting element and a moving element of the control cylinder on the side opposite the connection with the control pressure valve wherein the control pressure medium source is the hydrostatic pump and the auxiliary pump is driven by the primary energy source and wherein a pressure dependent reversing two way valve is provided having one inlet receiving fluid from the pressure dependent valve and delivering fluid to the operating cylinder, a hydrostatic transmission drive and a second inlet connected to a control pressure line which determines the setting of the hydrostatic power transmission drive unit.