Pressure balancing system for gear pumps or motors

Claim 2

A hydraulic pump, motor or the like comprising a housing assembly providing a gear chamber with high and low pressure ports communicating therewith at spaced locations, a pair of meshing gears in said chamber, a pressure plate adjacent each end of said gears, each pressure plate providing a seal face sealing with the adjacent end of said gears and a pressure force opposite said seal face, said gears when rotating entrapping and pressurizing liquid in a zone where the gears intermesh, pressure seal means in each pressure face operating when pressurized to produce a force urging the associated pressure plates toward sealing engagement with said gears, said seal means dividing said pressure faces into low pressure zones in communication with said low pressure port and high pressure zones in communication with said high pressure port, first passage means connected to supply entrapped liquid to pressurize said seal means, and second passage means smaller than said first passage means connecting one of said pressure zones and seal means for flow in both directions therebetween.

Claim 3

A hydraulic pump, motor or the like comprising a housing assembly providing a gear chamber with high and low pressure ports communicating therewith at spaced locations, a pair of meshing gears in said chamber, a pressure plate adjacent to at least one end of said gears, said pressure plate providing a seal face sealing with the adjacent end of said gears and a pressure face opposite said seal face, said gears when rotating entrapping and pressurizing liquid in a zone where the gears intermesh to a Pressure higher than the pressure in either of said pressure ports, pressure seal means in said pressure face operating when pressurized to produce a force urging said pressure plate toward sealing engagement with said gears, said seal means dividing said pressure face into a low pressure zone in communication with said low pressure port and a high pressure zone in communication with said high pressure port, first passage means connected to supply entrapped liquid to pressurize said seal means, and second passage means smaller than said first passage means connecting one of said pressure zones and seal means for flow in both directions therebetween, whereby the pressure in said seal means exceeds the pressure in said one of said pressure zones during operation.

Claim 4

A hydraulic pump, motor or the like comprising a housing assembly providing a gear chamber with high and low pressure ports communicating therewith at spaced locations, a pair of meshing gears in said chamber, a pressure plate adjacent to at least one end of said gears, said pressure plate providing a seal face sealing with the adjacent end of said gears and a pressure face opposite said seal face, said gears when rotating entrapping and pressurizing liquid in a zone where the gears intermesh to a Pressure higher than the pressure in either of said pressure ports, pressure seal means in said pressure face operating when pressurized to produce a force urging said pressure plate toward sealing engagement with said gears, said seal means dividing said pressure face into a low pressure zone in communication with said low pressure port and a high pressure zone in communication with said high pressure port, first passage means connected to supply entrapped liquid to pressurize said seal means, and second passage means smaller than said first passage means connecting one of said pressure zones and seal means for flow in both directions therebetween, whereby the pressure in said seal means exceeds the pressure in said one of said pressure zones during operation.

Claim 5

A hydraulic pump, motor or the like as set forth in claim 1 wherein said second passage means connects said high pressure zone to said seal means.

Claim 6

A hydraulic pump, motor or the like as set forth in claim 1 wherein said pressure plate is formed with a 3-shaped groove open through said pressure face, and said seal means is an elongated U-shaped resilient seal positioned in said groove.

Claim 7

A hydraulic pump as set forth in claim 4 wherein said first passage means includes a first pair of ports having a first predetermined diameter and said second passage means includes a second pair of ports having a diameter substantially equal to one-half of said predetermined diameter and said second pair of ports are open to said high pressure zones.

Claim 8

A hydraulic pump, motor or the like as set forth in claim 1 wherein said first passage means is open to entrapped liquid during a first portion of the entrapment, and said pressure plate is provided with relief means to release said entrapped liquid after it is no longer in communication with said first passage means.

Claim 9

A hydraulic pump, motor or the like as set forth in claim 6 wherein said relief means is a groove in said seal face along a central plane through the axes of said gears, and said first passage means are open through said seal face on the side of said central plane along which said intermeshing gears approach said central plane.

Claim 10

A hydraulic pump or the like as set forth in claim 7 wherein said gears operate to pump liquid from said low pressure port to said high pressure port, and said first passage means includes two passages open through said seal face on the high pressure side of said central plane.

Claim 11

A hydraulic pump or the like as set forth in claim 8 wherein said second passage means connects said high pressure zone and said seal means.

Claim 12

A hydraulic pump or the like as set forth in claim 7 wherein said gears are driven by liquid entering said high pressure port and exhausting from said low pressure port, and said first passage means includes two passages open through said seal face on the low pressure side of said central plane.

Claim 13

A hydraulic motor as set forth in claim 10 wherein said second passage means connects said high pressure zone and said seal means.

Claim 14

A hydraulic pump, motor or the like as set forth in claim 1 wherein said first passage means are ports located along a central plane containing the axes of rotation of said gears.

Claim 15

A hydraulic pump, motor or the like as set forth in claim 12 wherein said seal means is generally 8-shaped and is symmetrical with respect to said central plane.

Claim 16

A hydraulic pump, motor or the like as set forth in claim 13 wherein said seal means is provided with projections extending from the8-shaped portions in opposite directions therefrom.