Superheat control system

Claim 1

In a refrigerAtion system having a compressor, a condenser connected in fluid flow relation with the compressor by first conduit means, an expansion valve and an evaporator both being connected in fluid flow relation by second conduit means with the condenser, and with the evaporator being further connected in fluid flow relation with the compressor by third conduit means whereby refrigerant is made to flow from the compressor to the condenser, from the condenser to the expansion valve and therethrough to the evaporator, and from the evaporator back to the compressor to complete a refrigeration cycle, the improvement of a superheat control system embodied within the refrigeration system operable for sensing the superheat of the refrigerant flowing to the compressor and for performing a control function in response thereto, said superheat control system comprising: a. first pressure sensing means operable to establish a reference pressure, said first pressure sensing means including pipe means connected at one end thereof to the third conduit means in fluid flow relation therewith at a point along the length of the third conduit means adjacent to but spaced from the compressor and so as to comprise the sole fluid flow connection with the third conduit means between the point of connection of said pipe means with the third conduit means and the point of connection of the third conduit means with the compressor, said pipe means being operable to draw thereto from the third conduit means refrigerant at the same pressure and temperature conditions as the refrigerant entering the compressor from the third conduit means, said first pressure responsive means comprising a first pressure sensitive bellows expandable by the refrigerant received therewithin so as to thereby operate to establish a reference pressure therewithin corresponding to the pressure of the refrigerant within said first pressure sensitive bellows and therefore also to the pressure of the refrigerant entering the compressor from the third conduit means, said first pressure sensitive bellows including a first member connected thereto so as to be movable therewith in accordance with the expansion and contraction of said first pressure sensitive bellows; b. second pressure sensing means operable to establish a pressure correlated to the superheat of the refrigerant entering the compressor from the third conduit means, said second pressure sensing means including a sensing means having fluid therein supported in juxtaposed relation to the surface of the third conduit means adjacent to the point of connection of said pipe means with the third conduit means, said sensing means being operable to sense the superheat of the refrigerant flowing in the third conduit means and to establish by means of the fluid within said sensing means a pressure correlated to the sensed superheat, tube means having one end thereof connected to said sensing means for receiving fluid therefrom, and second pressure responsive means comprising a second pressure sensitive bellows having one end thereof connected to said tube means so as to receive fluid therefrom at a pressure corresponding to the pressure of the fluid within said sensing means, said second pressure sensitive bellows being expandable by the fluid received therewithin so as to thereby operate to establish a pressure therewithin correlated to the superheat of the refrigerant entering the compressor from the third conduit means as sensed by said sensing means, said second pressure sensitive bellows including a second member connected thereto so as to be movable therewith in accordance with the expansion and contraction of said second pressure sensitive bellows, said second pressure sensitive bellows being physically unconnected to said first pressure sensitive bellows so that the fluid within said second pressure sensitive bellows acts solely on said second pressure sensitive bellows and the refrigerant within said first pressure sensitive bellows acts solely on said first pressure sensitive Bellows; and c. switch means including a switch having at least one pair of contacts, at least one pair of terminals connected in electrical circuit relation with said pair of contacts and connectible in electrical circuit relation with an external electrical circuit for purposes of performing a control function, a contact member supported for movement between a first position and a second position relative to said pair of contacts, operating means mounted for movement between a first position and a second position operatively connected to said contact member for imparting movement thereto, said operating means comprising an elongated pivotably mounted lever arm having one end thereof mechanically connected to said contact member, said lever arm adjacent the other end thereof having said first member of said first pressure sensitive bellows in engagement therewith for applying a first force thereto in one direction corresponding to the reference pressure and also having said second member of said second pressure sensitive bellows in engagement therewith for applying a second force thereto in the opposite direction corresponding to the pressure correlated to the superheat of the refrigerant entering the compressor from the third conduit means wherein when said first force being applied to said lever arm by said first member of said first pressure sensitive bellows acting thereagainst exceeds said second force being applied to said lever arm by said second member of said second pressure sensitive bellows said lever arm is moved by the differential force being applied thereto to said first position thereof causing said contact member to occupy said first position thereof relative to said pair of contacts and when said first force being applied to said lever arm by said first member of said first pressure sensitive bellows is less than said second force being applied to said lever arm by said second member of said second pressure sensitive bellows said lever arm is moved by the differential force being applied thereto to said second position thereof thereby causing said contact member to occupy said second position thereof relative to said pair of contacts.