The inventor has found that 5 degrees for the angle between the two rotating parts is the optimal angle to provide an operable pump, but not enough to require the use of bearings.

1) Piston Block 2) Cylinder Drum 3) Piston Shaft 4) Five degree angled control surface 5) End Plate 6 & 7) Ports 8) Drive Shaft 9) Piston Head

Photos provided by the inventor

Cylinder drum.

Wolfhart rotor.

Although this pump has no oscillating motion (when viewed from a stationary reference system), it works as though it does. This is illustrated in these two matching video clips of a working pump with its outer housing removed. The upper clip shows the view in the stationary reference system, which shows that both moving parts just rotate. In the lower clip the view is as though the camera were orbiting the pump at a matched rotational speed. By using this view, it is as if we are "within" the co-rotating system (sort of like observing other planets in our solar system from our own, which is also revolving). In this way can we observe the oscillating motion between a piston and its cylinder.

(Note: A central pin and spring keeps the cylinder block in position on the "control surface" (where the ports are) when the pump is not being operated or is running without any pressure. The spring assemblies seen encircling the pistons in some photos are not necessary for effective pump operation. They hold the piston heads in place, but only up to a limited amount of force. If a piston seizes in a cylinder, the spring will oscillate until the piston loosens up or the pump is stopped. Even with a stuck piston head, the pump can usually continue to operate at reduced capacity.)

Video clips provided by the inventor

This shows the pump from the "point of view" of one piston.

(This is a still representation and possibly also a low-resolution image of a pump which is fully animated in the CD-ROM version of this glossary.)

The pistons work during the first half (intake portion) of each cycle, when they "suck" fluid in against the high pressure in the housing. Fluid does not get its energy by being "pushed out" by the pistons, which are actually free-floating (doing nothing, not even sealing) during the second half of their cycle. (The pump outlet can actually be anywhere on the housing.)

Showing the intake and outlet ports.

According to the inventor, the existence of high pressure in the housing is necessary for pressure balancing of the two rotors.

At first glance this pump might appear to be a bent axis pump. However, bent axis pumps usually have more than a 5 degree angle -- and bearings on the piston rods. This pump can also be compared to the radial piston pump, swash plate pump, the wobble pump, and the ball piston pump, as one or more of its principles are also seen in these other pumps.

After decades of research and several prior related patents and patent applications, on Nov. 28th, 2000, Wolfhart Willimczik, Bradenton, FL, received patent #6,152,014 from the U.S. Patent Office, covering "ROTARY PISTON MACHINES". Here is the patent's abstract:

This invention relates to rotary piston machines with a positive displacement principle, pressure-tight work chambers and a strong piston actuating mechanism without power transmitting bearings. A piston rotor is rotationally coupled via its pistons or plungers, which reciprocatingly move in the cylinders of a cylinder rotor. Both axial and radial machines are included having a short stroke motion, but only in a co-rotating system. No oscillating mass power exists. This new piston actuating concept is applicable for all machines having at least one rotating pair of piston and cylinder. On top of the wide variety is an axial piston machine with a self-aligning pulling piston actuating mechanism and a quasi complete hydrostatic pressure balance of all movable parts including an outgoing shaft. This invention allows the building of machines, such as water hydraulic motors, pumps, vacuum pumps, and dry running or water-sealed compressors etc, for any reasonable parameter, such as high pressure, high volume, and any reasonable speed without necessarily lubricating said machines. Practice confirms that such machines are the State-of-the-Art in this field. Combinations of two or more machines in one housing, and with one shaft only, are possible also, for instance a motor and a pump for energy recovery systems etc. All these machines are not only able to work completely oil-free and are environmentally friendly, but they also operate at the highest performance combined with a high efficiency.