Abstract:
Solenoid controlled hydraulic valves in sealed hydraulic circuits are provided with backup actuation without compromise of the hydraulic circuit by provision of an auxiliary, quick fitting solenoid coil case which incorporates manual switches and which may be attached directly to a battery for energization.

Description:
BACKGROUND OF THE INVENTION 
   1. Technical Field 
   The invention relates in general to solenoid control elements for hydraulic valves and more particularly to a quick fitting replacement solenoid for use as a diagnostic tool or backup actuator for a spool type hydraulic valve in a closed hydraulic circuit. 
   2. Description of the Problem 
   Vehicle mounted hydraulic systems have been employed for diverse purposes including positioning snowplows, compacting trash, moving support beds and other functions. Such hydraulic systems are controlled using spool valves and these spool valves in turn have often been manually activated, with handles mechanically linked to the spool valves. The mechanical link must of course be sealed to avoid spillage of pressurized hydraulic fluid. However, these seals are prone to wear and leaks almost invariably develop. 
   To avoid, or at least postpone, the development of leaks, solenoid controlled hydraulic valves have been developed. A solenoid coil is used to generate magnetic fields to control positioning of the spool valve inside the valve body without the need for a mechanical linkage through the valve body. Without a mechanical linkage, the need for mechanical seals around a linkage is eliminated. Solenoid actuated valves are much less prone to leakage than mechanically actuated valves, but they complicate making provision for fitting an override control mechanism to the valve. Some manufacturer&#39;s have retained a mechanical linkage to use as a backup to the electromagnetic system. While the linkages are now used less often, they still represent a compromise of the full sealing of the hydraulic system, and they can still develop leaks over time due to thermal cycling or chemical attack. The use of solenoids also eases integration between a vehicle&#39;s hydraulic systems and the vehicle&#39;s electronic control systems. This in turn raises questions in some minds as to the reliability of the electronic controls or the ability to diagnose a problem as being electronic or hydraulic, should a problem occur. 
   SUMMARY OF THE INVENTION 
   According to the invention there is provided a solenoid coil and valve assembly having an hydraulic valve body having a rod like extension. The solenoid coil is held within a tube shaped coil case sized and shaped to fit over and around the rod like extension after removal of the original coil assembly. An electrical switch carrier is mounted to an outside surface of the tube shaped coil case. Electrical leads from the switch body provide for direct, temporary connection to a battery. 
   Additional effects, features and advantages will be apparent in the written description that follows. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself however, as well as a preferred mode of use, further objects and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein: 
       FIG. 1  is a perspective view of a prior art solenoid controlled hydraulic valve assembly. 
       FIG. 2A  is a perspective view of an solenoid controlled hydraulic valve assembly according to the present invention. 
       FIG. 2B  is a circuit schematic for the solenoid controller. 
       FIG. 3  is an exploded view of a solenoid controller and a hydraulic valve. 
       FIG. 4  is a partial cross sectional view of the solenoid controlled hydraulic valve assembly of  FIG. 2 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to the figures and in particular to  FIG. 1 , a prior art solenoid controlled hydraulic valve assembly  10  is shown comprising a hydraulic valve, the stem  12  of which is visible extending below a coil package  14 . 
   Coil package  14  is substantially self contained, providing only inputs for connection to an electronic control system. Coil package  14  provides bidirectional control of the valve. Coil package  14  fits over the upper end of valve body  18  and is retained on valve body  18  using a nut  16  threaded onto a threaded upper end of valve body  18 . A nut  20  threaded onto the lower a middle threaded section  22  of valve body  18  positions double ended coil package  14 . 
   Referring to  FIG. 2A  a replacement solenoid body  24  is a tube like structure, fitted over valve body  18  to provide manual control over the valve. Switches  32 ,  34  are disposed on a switch box  26  which in turn is carried on the outside surface of the replacement solenoid body  24 . Switches  32 ,  34  provide for manual energization of the solenoid coil  44 . Switch box  26  has electrical leads  28  which are intended for direct connection to a 12 volt battery, such as the motor vehicle battery or an auxiliary battery. A quick release button  30  extends from the replacement solenoid body  24  near the upper rim of the solenoid body. The circuit for the solenoid  44  of  FIG. 2B  may be represented as a bridge circuit connected across a battery  60 . External buttons  32  and  34  correspond to switch sets  132  and  134 , respectively, which are arranged to energize coil  44  in either of two directions. 
   As seen in  FIG. 3 , replacement solenoid body  24  fits around an upper rod like segment  42  of valve body  18  and may be fitted with a quick release mechanism released by button  30  which cooperates with threads  40  for retaining body  24  on rod  42 . The partial cross section of  FIG. 4  better illustrates that replacement valve body  24  is a tube, constructed from a casing  46  which contain coils  44  in its interior. Coils  44  are energized by use of switch box  26 . Switch box  26  contains two momentary switches used for bidirectional control of the spool valve (not shown) disposed inside valve body  26 . The quick release mechanism  30  extends through casing  46  and cooperates with threading  50  at the top end of rod  42 . 
   The invention gives operators the confidence that they can move to electronics controlled hydraulic systems, with a fully sealed hydraulic system, without losing the ability to manually control valves using a direct, simple, electrical system. Mechanical backups to electronic solenoid valve control is eliminated. 
   While the invention is shown in only one of its forms, it is not thus limited but is susceptible to various changes and modifications without departing from the spirit and scope of the invention.